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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymer composition having excellent
compatibility composed of (A) starch and (B) vinyl alcohol polymer having
an alkyl group of 4 to 50 carbon atoms at the terminal.
The present invention relates further to a polymer composition having
excellent compatibility composed of (A) starch, (B) vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal, and (C)
polyvinyl alcohol.
The present invention relates also to a textile sizing agent which gives
yarn good weavability. More particularly, it relates to a textile sizing
agent to give yarn good weavability, which is composed of (A) starch, (B)
vinyl alcohol polymer having an alkyl group of 4 to 50 carbon atoms at the
terminal, (C) polyvinyl alcohol, and (D) oil for textile sizing.
2. Description of the Prior Art
A mixture of starch and polyvinyl alcohol (abbreviated as PVA hereinafter)
has a usage for warp sizing and paper sizing because it is water-soluble
and good in film-forming performance and natural starch is water-soluble
and readily available at a low price. However, it has some disadvantages:
A mixed aqueous solution of starch and PVA is so unstable as to cause the
separation of solutes, because of the poor compatibility of starch and
PVA, which are both polymeric compound. In addition, it forms a film which
is poor in transparency and other film properties.
For the improvement of the compatibility of starch and PVA, many attempts
were made to use various kinds of modified starch (including starch
derivatives such as etherified starch, esterified starch, and cationized
starch; and decomposition products of starch such as oxidized starch and
dextrin). Starch derivatives are expensive and decomposition products of
starch have a disadvantage ascribed to their lower molecular weight than
natural starch. That is, a mixed aqueous solution of a decomposition
product of starch and PVA is stable but does not provide a film of good
properties. In other words, these starch derivatives and decomposition
products of starch are not satisfactory in compatibility with PVA.
On the other hand, it is known that modified PVA copolymerized with
monomers having long-chain alkyl groups of 4-20 carbon atoms has improved
compatibility with natural starch. ( Japanese Patent Laid-open Nos.
4544/1981 and 55440/1981.) A mixed aqueous solution of the modified PVA
and starch is stabler than that of unmodified PVA and starch.
Nevertheless, it easily gels and does not form a film of satisfactory
properties. Furthermore, the modified PVA is not effective for the
above-mentioned modified starch.
As for PVA, there is known a process for producing a vinyl alcohol polymer
having a long-chain alkyl group at the terminal. (See Japanese Patent
Publication No. 1831/1973 and Japanese Patent Laid-open No. 108207/1983.)
However, nothing is known about the compatibility of this vinyl alcohol
polymer with starch.
In the meantime, there is an ever-increasing demand for a warp size having
higher performance than before. The warp size has become necessary for
high-speed weaving and production of high-quality textiles since the
advent of modern looms including shuttle looms, gripper looms, rapier
looms, water jet looms, and air jet looms, which are used for weaving
natural fibers (such as cotton and wool), semisynthetic fibers ( such as
rayon, acetate and etc.) , and synthetic fibers (such as nylon, polyester,
and acrylic).
To make a sizing agent for warp sizing, starch, PVA, and acrylic size are
used individually or in combination with one another. They are also used
in combination with oil for textile sizing and carboxymethylcellulose. PVA
is most popular among them, and it is used in the form of completely
saponified PVA, partially saponified PVA, anion-modified PVA, or
cation-modified PVA or other modified PVA. Modified PVA in which a
hydrophobic group is copolymerized is also known( as disclosed in Japanese
Patent Laid-open Nos.55440/1981 and 174683/1983). They are all intended to
improve the adhesion of a sizing agent to hydrophobic fibers such as
polyester and nylon, thereby to improve the cohesive force and abrasive
resistance and to reduce the yarn hairiness.
There are known processes for producing a vinyl alcohol polymer having a
long-chain alkyl group at the terminal( as disclosed in Japanese Patent
Publication No. 1831/1973 and Japanese Patent Laid-open Nos. 108207/1983
and 102946/1984). It is also known that the vinyl alcohol polymer has
improved abrasive resistance due to a low coefficient of friction(as
disclosed in Japanese Patent Publication No. 22218/1969) and the vinyl
alcohol polymer can be used for the surface modification of molded
items(as disclosed in Japanese Patent Publication No. 18258/1971).
A warp sizing agent for spun yarns is usually composed of PVA and starch.
PVA is preferred because of its stable quality attributable to its being a
synthetic polymer, its good film-forming performance and ability to form
film of good properties, and its good adhesion to fibers. Starch is
preferred because of its low price and its ready availability. The
disadvantage of this sizing agent is that PVA and starch are poor in
compatibility with each other because they are both polymeric compounds.
Therefore, a mixed aqueous solution of PVA and starch is so unstable that
PVA and starch readily separate from each other. Moreover, the aqueous
solution of PVA and starch becomes poor in sizing performance after
standing for a couple of days to such an extent that it cannot be used
again.
PVA and starch are often used in combination with acrylic size, oil for
textile sizing, and/or CMC. Oil for textile sizing is used to (1) make
smooth the yarn surface, (2) promote the infiltration of the size
solution, (3) make the sized yarn hygroscopic, (4) impart antistatic
properties, (5) prevent the yarn from sticking to the drying cylinder of
the sizing machine, (6) make the yarn soft, and (7) improve the yarn
handling. Oil for textile sizing includes various vegetable oils, paraffin
wax, and surface active agents. Paraffin wax and vegetable oils are
generally used where (1),(5),(6) and(7) are the major objectives. They are
emulsified and dispersed into water by an emulsifier (a nonionic or ionic
surface active agent). Nevertheless, they are essentially poor in
compatibility with PVA and starch and the sizing solution thereof is poor
in stability. The film formed from the sizing solution is not uniform in
quality and poor in strength and elongation, although it softens the yarn.
Elongation is so low that the film as a whole is brittle and poor in
abrasive resistance. Thus, the sizing agent is not suitable for warps to
be woven into high-quality textiles or to be woven on a high-speed loom
such as air jet loom.
There is a warp sizing agent based on anion-modified PVA, cation-modified
PVA, or PVA copolymerized with a hydrophobic group. This sizing agent,
when dissolved in water by heating, forms a stable sizing solution; but
the stability is not still satisfactory. The film formed after drying of
the size solution is not completely uniform. Therefore, this sizing agent
is not satisfactory in weavability where high-quality textiles and
high-speed looms are involved.
Another means to improve the compatibility is to add an acrylic size to a
mixture of PVA, starch and oil for textile sizing. However, the
improvement in compatibility is insufficient.
SUMMARY OF THE INVENTION
With the above-mentioned in mind, the present inventors carried out a
series of researches which led to the findings mentioned below.
(A) starch and (B) vinyl alcohol polymer having an alkyl group of to 50
carbon atoms at the terminal are compatible with each other ,and a polymer
composition composed of them(referred to as polymer composition (I)
hereinafter) forms a stable aqueous solution which remains almost
unchanged in viscosity with time and the aqueous solution provides a
transparent film having good film properties.
When the polymer composition (I) is incorporated with (C) PVA, the
When the polymer constituents in the resulting composition (referred to as
polymer composition (II) hereinafter) are compatible with one another, and
it forms a stable aqueous solution which remains almost unchanged in
viscosity with time and the aqueous solution provides a transparent film
having good film properties.
In addition, when a sizing agent composed of (A) starch, (C) PVA, and
(D)oil for textile sizing is incorporated with (B) vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal, the
compatibility of starch and PVA improves and the emulsification and
dispersion of oil for textile sizing also improve, and the resulting
sizing agent is stable and provides uniform film. The yarn sized by this
sizing agent shows an excellent elongation, softness, and abrasive
resistance, and the reduced yarn hairiness.
The present invention was completed on the basis of these findings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph in which the viscosity of an aqueous solution of polymer
composition (I) ( which is a mixture of corn starch and vinyl alcohol
polymer having an alkyl group of 4 to 50 carbon atoms at the terminal or
ordinary PVA ) is plotted against the content of vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal or ordinary
PVA. The abscissa (X) represents the content (wt %) of vinyl alcohol
polymer having an alkyl group of 4 to 50 carbon atoms at the terminal or
ordinary PVA in the total solids. The ordinate (Y) represents the
viscosity of the aqueous solution measured with a Brookfield viscometer at
20.degree. c. The solid line (1) represents the results obtained with
solutions containing corn starch and vinyl alcohol polymer . having an
alkyl group of 4 to 50 carbon atoms at the terminal, and the broken line
(2) represents the results obtained with solutions containing corn starch
and ordinary PVA ("Kuraray PVA-105")
FIG. 2 is a graph in which the transmittance of an aqueous solution of the
polymer composition (I) ( which is a mixture of oxidized starch and vinyl
alcohol polymer having an alkyl group of 4 to 50 carbon atoms at the
terminal or modified PVA copolymerized with monomer having long-chain
alkyl group or ordinary PVA ) is plotted against the content of vinyl
alcohol polymer having an alkyl group of 4 to 50 carbon atoms at the
terminal or modified PVA copolymerized with monomer having long-chain
alkyl group or ordinary PVA. The abscissa (X) represents the content (wt
%) of vinyl alcohol polymer having an alkyl group of 4 to 50 carbon atoms
at the terminal or modified PVA copolymerized with monomer having
long-chain alkyl group or ordinary PVA in the total solids. The ordinate
(Y) represents the transmittance of the aqueous solution at 20.degree. c.
The solid line (1) represents the results obtained with solutions
containing oxidized starch and vinyl alcohol polymer having an alkyl group
of 4 to 50 carbon atoms at the terminal, and the broken line (2)
represents the results obtained with solutions containing oxidized starch
and modified PVA copolymerized with monomer having long-chain alkyl group,
and the chain line (3) represents the results obtained with solutions
containing oxidized starch and PVA-105.
FIG. 3 is a graph in which the transmittance of an aqueous solution of the
polymer composition (11) ( which is a mixture of vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal or modified
PVA copolymerized with monomer having long-chain alkyl group, oxidized
starch and PVA) is plotted against the content of vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal or modified
PVA copolymerized with monomer having long- chain alkyl group or PVA-105.
The abscissa (X) represents the content (wt %) of vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal or modified
PVA copolymerized with monomer having long-chain alkyl group or PVA-105 in
the total solids. The ordinate (Y) represents the transmittance of the
aqueous solution at 20 .degree. c. The solid line (1) represents the
results obtained with solutions containing oxidized starch and vinyl
alcohol polymer having an alkyl group of 4 to 50 carbon atoms at the
terminal , and the broken line (2) represents the results obtained with
solutions containing oxidized starch and modified PVA' copolymerized with
monomer having long-chain alkyl group, and the chain line (3) represents
the results obtained with solutions containing oxidized starch and PVA-105
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
At first, a description is made of polymer composition (I) in the invention
which is composed of (A)starch and (B) vinyl alcohol polymer having an
alkyl group of 4 to 50 carbon atoms at the terminal
Polymer composition (I) in the invention contains (B)vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms(hydrophobic group) at the
terminal (referred to as terminal-modified PVA hereinafter), which is
described in the following.
The terminal long-chain alkyl group should be one which has 4 to 50 carbon
atoms. With carbon atoms less than 4 , the terminal-modified PVA is not so
different from unmodified PVA and is not satisfactorily compatible with
starch. With carbon atoms more than 50, the terminal-modified PVA is
excessively hydrophobic and is poor in water solubility. As the results,
it is poor in compatibility with starch. Therefore, the number of carbon
atoms should be 4 to 50, preferably 8 to 24. Examples of such alkyl groups
include straight-chain alkyl groups, branched-chain alkyl groups, and
alkylaryl groups each having 4-50 carbon atoms. They may contain O, N,
S-atom etc.
The polymer should have a degree of polymerization in the range of 10 to
3000, preferably 50 to 2500, depending on the amount of terminal groups
introduced during the polymerization reaction. The polymer is not limited
in the degree of saponification: but it is usually not less than 50 mol %,
preferably not less than 70 mol %.
The polymer may contain vinyl alcohol units, vinyl ester units such as
vinyl acetate units, and a small amount of copolymer units. Examples of
the copolymer units include .alpha.-olefins such as ethylene, propylene,
and isobutene; unsaturated carboxylic acid such as acrylic acid,
methacrylic acid, crotonic acid, maleic acid, itaconic acid, and maleic
anhydride, and salts thereof and alkyl esters thereof; acrylonitrile,
methacrylonitrile, acrylamide, methacrylamide, alkylvinyl ether,
N,N-dimethylacrylamide, N-vinylpyrrolidone, vinyl chloride, vinylidene
chloride, vinyl propionate, vinyl ester of Versatic acid, and
2-acrylamidepropanesulfonic acid and salt thereof. They are not
limitative.
The terminal-modified PVA (B) can be produced in several manners. According
to a preferred process for industrial production, a monomer composed
mainly of vinyl ester (such as vinyl acetate) is polymerized in the
presence of mercaptan having an alkyl group of 4 to 50 carbon atoms and
the resulting polyvinyl ester is saponified in the usual way.
The starch (A) is one which comes from wheat, corn, rice, potatoes, sweet
potatoes, tapioca, and sago palm. Among them, wheat starch and corn starch
are adequate. The starch may be used in the form of starch derivative such
as dextrin, oxidized starch, etherified starch, esterified starch, and
cationized starch.
The mixing ratio of (B) terminal-modified PVA to (A) starch is 0.5-10000
parts by weight, preferably 5-2000 parts by weight for 100 parts by weight
of (A).
Where the major objective is to improve the stability of the aqueous
solution of starch, the mixing ratio of (B) to (A) should be not less than
0.5, preferably not less than 5 (in parts by weight) for 00 parts by
weight of (A). The terminal-modified PVA (B) in an amount less than 0.5
parts by weight for 100 parts by weight of starch (A) is not sufficient to
produce a desired effect. Where the major objective is to improve the
quality of starch film, the amount of (B) should be not less than 10 parts
by weight, preferably not less than 20 parts by weight, for 100 parts by
weight of (A).
If the amount of starch (A) is less than 1 part by weight for 100 parts by
weight of terminal-modified PVA (B), the resulting mixture is
substantially identical with (B) alone.
The polymer composition (I) of the invention which is composed of (A)
starch and (B) terminal-modified PVA has the following features.
The polymer composition (I) provides an aqueous solution which is clearer,
stabler (with less change in viscosity after standing), and easier to
handle than an aqueous solution of a mixture of starch and an ordinary PVA
(such as PVA, anion-modified PVA, cation-modified PVA, non ion-modified
PVA, and other modified PVA). Presumably, this is because starch is
uniformly dispersed in water without agglomeration on account of the
extremely good compatibility of (A)starch and (B) terminal-modified PVA.
In the case of a PVA copolymer in which long-chain alkyl groups are
randomly copolymerized, the aqueous solution containing a PVA copolymer in
which long-chain alkyl group are randomly copolymerized and starch is
slightly improved in stability, but is not so stable as the aqueous
solution of polymer composition (I) of the present invention.
The viscosity of the mixed aqueous solution of (A) starch and (B)
terminal-modified PVA suggests the presence of a unique interaction
between (A) and (B). This was experimentally proved as follows: Aqueous
solutions were prepared by dissolving in water 5 wt % of corn starch and
varied amount of terminal-modified PVA having a C.sub.12 H.sub.25 -alkyl
group, a degree of polymerization of 100, and a degree of saponification
of 99.2 mol %, followed by cooking at 95 .degree. c for 2 hours with
stirring. The viscosity of the aqueous solutions was measured at
90.degree. C. using a Brookfield viscometer. The same experiment was
repeated except that the terminal-modified PVA was replaced by "Kuraray
Poval PVA-105" having a degree of polymerization of 550 and a degree of
saponification of 98.5 mol %. The results are shown in FIG. 1.
In FIG. 1, the solid line (1) represents the results obtained with
solutions containing corn starch and terminal-modified PVA, and the broken
line (2) represents the results obtained with solutions containing corn
starch and PVA-105. It is noted that in the case of corn starch/PVA-105
aqueous solutions, the viscosity decreases as the PVA content increases.
By contrast, in the case of aqueous solutions containing corn starch and
(B) terminal-modified PVA has generally a higher viscosity than the corn
starch/ PVA-105 aqueous solutions (despite the fact that the viscosity of
aqueous solutions of (B) terminal-modified PVA alone is lower than that of
aqueous solutions of PVA-105). Moreover, the viscosity reaches the maximum
when the content of (B) terminal-modified PVA is 10-30 wt %. This fact
apparently indicates the unique interaction between corn starch and (B)
terminal-modified PVA.
A modified PVA formed by copolymerizing with long-chain alkyl groups
improves the stability of the mixed aqueous solutions; but it does not
prevent gelation completely. In addition, it is not effective for modified
starch. Unlike a modified PVA formed by copolymerizing with long-chain
alkyl group, the terminal -modified PVA(B) has the good surface activity
on account of the hydrophobic terminal long-chain alkyl group and the
hydrophilic PVA moiety which are connected blockwise. It is considered
that the terminal long-chain alkyl group improves the compatibility with
starch and the PVA moiety promotes the dispersion into water. This is what
differentiates the terminal-modified PVA from the modified PVA randomly
containing long-chain alkyl groups.
Polymer composition (I) of the present invention is characterized by that
the aqueous solution of it changes in viscosity very little with time.
This suggests that the starch in it is protected from deterioration.
Starch is composed of amylose and amylopectin, and starch deterioration is
caused by the crystallization of amylose. It is known that amylose is
compatible with a fatty acid because of their interaction.
The terminal-modified PVA is also interactive with amylose because of the
terminal long-chain alkyl group similar to a fatty acid. The PVA moiety
facilitates the dispersion into water. Presumably, this is the reason why
the starch is protected from deterioration.
It was found that the terminal-modified PVA (B) used in the present
invention interacts with amylopectin. (This had not been known well
before.) This interaction was confirmed by the following experiment.
Amylopectin isolated from corn starch was mixed at varied ratios with a
vinyl alcohol polymer having a C.sub.12 H.sub.25 alkyl group at the
terminal, a degree of polymerization of 280, and a degree of
saponification of 98.5 mol %. The resulting mixtures were dissolved in
water, followed by cooking at 95.degree. c for 2 hours. Thus there were
obtained 1.5wt % aqueous solutions containing vinyl alcohol polymer having
a C.sub.12 H.sub.25 alkyl group at the terminal and amylopectin. The
Brookfield viscosity and transmittance of the aqueous solutions were
measured at 20 .degree. c.[Transmittance was measured at a wavelength of
650 nm and a cell width of 10 mm using a spectrophotometer (made by
Hitachi Ltd.)]
The results are shown in Table 1.
TABLE 1
______________________________________
Terminal-modified
PVA (wt %)* 0 10 20 30 50
______________________________________
Viscosity (centipoise)
8 10 12 14 17
Transmittance (%)
18 20 30 42 50
______________________________________
*Ratio of terminalmodified PVA in the total solids.
It is noted from Table 1 that both viscosity and transmittance increase as
the amount of the terminal-modified PVA (B) increases. Incidentally, the
viscosity of an aqueous solution containing 1.5 wt % of the
terminal-modified PVA(B) alone is as same as water having a viscosity of
about 1 centipoise.
The same experiment was performed except that ordinary PVA("Kuraray Poval
PVA-105") was used in place of the terminal-modified PVA.
In the case of aqueous solutions containing amylopectin and ordinary PVA
("Kuraray Poval PVA-105") having a degree of polymerization of 550 and a
degree of saponification of 98.5 mol %, viscosity was about 8 centipoise
and transmittance was 16-18% regardless of the amount of PVA-105. This
result suggests the presence of a characteristic interaction between the
terminal-modified PVA (B) and amylopectin. Such an interaction is not
observed in the case of ordinary PVA, modified PVA copolymerized with
long-chain alkyl groups and other modified PVA.
The fact that the terminal-modified PVA (B) interacts with amylose as well
as amylopectin is considered to be the reason why it is compatible with
not only natural starch but also oxidized starch and other modified
starch.
The aqueous solution of polymer composition(I) of the invention provides an
extremely uniform, clear film which is superior in strength and elongation
to film formed from an aqueous solution containing starch and ordinary
PVA.
Presumably, this is because the terminal long-chain alkyl group enhances
the interaction with starch and the hydrophilic PVA moiety prevents the
agglomeration of starch particles and keep them uniformly dispersed. This
effect is pronounced by the blockwise construction of the hydrophobic
long-chain alkyl group and the hydrophilic PVA moiety.
The mixing of (A) starch and (B) terminal-modified PVA is accomplished in
any way. According to one way, the two components are mixed in powder form
and the resulting mixture is added to water , or water is added to the
resulting mixture, and then heated and dissolved. Alternatively, the two
components are heated separately in water and the resulting solutions are
mixed with each other.
The thus formed mixture may be incorporated with plasticizers, coloring
agents, fillers, salts, boric acid or borax, water-soluble polymers,
surface active agents, and other additives.
Polymer composition (I) of the invention can be used as a textile sizing
agent, particularly warp sizing agent, paper finishing agent, adhesive,
and stock for film making.
What follows is a description about polymer composition (II) of the present
invention which is composed of (A) starch, (B) vinyl alcohol polymer
having an alkyl group of 4 to 50 carbon atoms at the terminal
(terminal-modified PVA) and (C) polyvinyl alcohol.
The (A) and (B) components are the same as those used in the abovementioned
polymer composition (I).
The third component, (C) polyvinyl alcohol (abbreviated as PVA), may be
ordinary PVA having a degree of polymerization of 100-3000 , preferably
200-2500, and a degree of saponification not less than 50 mol %,
preferably not less than 70 mol %. In addition, it may also be
anion-modified PVA, cation-modified PVA, or nonion-modified PVA.
The formulation of polymer composition (11) of the invention varies over a
broad range. The total amount of components [(B)+(C)] should be 2-10000
parts by weight, preferably 5-5000 parts by weight, for 100 parts by
weight of component (A). If the total amount of component[(B)+(C)] is less
than 2 parts by weight, the resulting composition has the same properties
as those of starch. If the total amount of components (B)+(C)] is more
than 10000 parts by weight, the resulting composition does not permit
starch to produce its effect. The amount of component (C) should be
1-10000 parts by weight, preferably 1-5000 parts by weight, for 100 parts
by weight of component (B).
The amount of component (B) should be 1-3000 parts by weight, preferably
5-1000 parts by weight, for 100 parts by weight of component (A). Where
the major objective is to improve the stability of the aqueous solution of
starch, the amount of component (B) should be not less than 1 part by
weight, preferably not less than 5 parts by weight, for 100 parts by
weight of component (A). If the amount of component (B) is less than 1
part by weight, the effect of component (B) is modest. Where the major
objective is to improve the quality of starch film, the amount of
component (B) should be not less than 10 parts by weight, preferably not
less than 20 parts by weight, for 100 parts by weight of component (A). If
the amount of component (B) is in excess of 5000 parts by weight for 100
parts by weight of component (A), the effect of component (A) is not
produced.
Polymer composition (II) composed of (A) starch, (B) terminal-modified PVA,
and (C) PVA has the following characteristic features.
Polymer composition (II) provides an aqueous solution which is clearer,
stabler (with less change in viscosity after standing), and easier to
handle than an aqueous solution of a mere mixture of starch (A) and PVA
(C). Presumably, this is because starch (A) and terminal-modified PVA (B)
are compatible with each other and starch particles ar kept uniformly
dispersed in an aqueous solution without
e agglomeration. In addition, the terminal-modified pVA (B) and PVA (C) are
considerably compatible with each other and consequently all the
components are satisfactorily compatible with one another and the solution
as a whole is stable. In the case of a modified PVA in which long-chain
alkyl groups are randomly copolymerized, the aqueous solution containing
this modified PVA and starch is slightly improved in stability as compared
with the composition containing ordinary PVA, but is unstable than the
aqueous solution of polymer composition (II) of the present invention.
The aqueous solution of polymer composition (II) of the invention provides
an extremely uniform, clear film which is superior in strength and
elongation to film formed from an aqueous solution containing only starch
(A) and PVA (C).
Presumably, this is because the terminal long-chain alkyl group in the
terminal-modified PVA (B) enhances the interaction with starch (A) and the
hydrophilic PVA moiety in the terminal-modified PVA (B) prevents the
agglomeration of starch particles and it has a good compatibility with
PVA(C), therefore starch is uniformly dispersed in the form of fine
particles. This effect is pronounced by the blockwise construction of the
hydrophobic long-chain alkyl group and the hydrophilic PVA moiety.
The mixing of (A) starch, (B) terminal-modified PVA ,and (C) PVA is
accomplished in any way. According to one way, the three components are
mixed in powder form and the resulting mixture is added to water, or water
is added to the resulting mixture. Alternatively, the three components are
heated separately in water and the resulting solutions are mixed with one
another. The cooking of natural starch may be accomplished under either
atmospheric pressure or high pressure; but the latter is preferable.
The thus formed mixture may be incorporated with plasticizers, coloring
agents, fillers, salts, boric acid or borax, water-soluble polymers,
surface active agents, and other additives.
Polymer composition (II) of the invention can be used as a textile sizing
agent, particularly warp sizing agent, paper finishing agent, adhesive,
and stock for film making.
The textile sizing agent made of the polymer composition of the invention
is composed of (A) starch, (B) vinyl alcohol polymer having an alkyl group
of 4 to 50 carbon atoms at the terminal (terminal-modified PVA), (C) PVA
and (D) oil for textile sizing, as explained in the following.
The (A), (B)and (C) components are the same as those used in the
above-mentioned polymer compositions (I) and (II).
The oil for textile sizing (D) is a vegetable oil, paraffin wax, or surface
active agent. It is intended to make the sized yarn smoother, to impart
softness, to prevent sized yarn from sticking to the drying cylinder, and
to improve yarn handling. A vegetable oil or paraffin wax is mainly used.
The mixing ratio of (A) starch, (B) terminal-modified PVA, (C) PVA, and (D)
oil for textile sizing is explained below
The amount of component (A) should be 10-1900 parts by weight, for 100
parts by weight of components [(B)+(C)] in total. If the amount of
component (A) is less than 10 parts by weight, the resulting sizing agent
is not satisfactory in dividability; and if it is in excess of 1900 parts
by weight, the resulting sizing agent forms film of poor properties and is
poor in weavability.
The amount of component (D) should be 0.1-200 parts by weight for 100 parts
by weight of components [(B)+(C)] in total. If the amount of component (D)
is less than 0.1 parts by weight, the oil does not produce any effect; and
if it is in excess of 200 parts by weight, the resulting sizing agent
forms film of poor properties and is poor in weavability.
The amount of PVA (C) should be 0-10000 parts by weight for 100 parts by
weight of component (B).
The amount of terminal-modified PVA (B) should be not less than 1 part by
weight, preferably not less than 3 parts by weight , for 100 parts by
weight of starch (A). With an amount less than 1 part by weight, no effect
is produced.
The amount of terminal-modified PVA(B) should be not less than 0.1 parts by
weight, preferably not less than 1 part by weight , for 100 parts by
weight of oil for textile sizing(D). With an amount less than 0.1 parts by
weight, no effect is produced for the emulsification and dispersion of oil
for textile sizing.
A mixture containing (A) starch, (C) PVA, and (D) oil for textile sizing
becomes stable when it is incorporated with (B) terminal-modified PVA. The
terminal-modified PVA improves the emulsification and dispersion of oil
for textile sizing (paraffin wax or vegetable oil) and prevents the phase
separation of the size solution and stabilizes the viscosity of the size
solution. The size solution thus prepared provides extremely uniform film.
If oil for textile sizing (D)(vegetable oil or paraffin wax) is added in
the absence of terminal-modified PVA, the resulting size solution is
unstable because it is poor in compatibility with (A)starch and (C) PVA.
And the resulting size solution tends to provides uneven film having a low
elongation. By contrast, the terminal-modified PVA(B) permits oil for
textile sizing to uniformly disperse with the result that the size
solution has improved stability and fluidity and provides uniform film.
The thus formed film has a good elongation which tends to increase as the
content of wax in the sizing agent increases up to 10-12 wt %.
The microscopic observation of the film reveals that paraffin wax or
vegetable oil is distributed in the form of uniform fine particles
Presumably, the emulsification and dispersion may be attributable to the
high surface activity of terminal-modified PVA (B). However, this
remarkable effect is not produced in the case of modified PVA formed by
copolymerizing with monomer having hydrophobic groups. This suggests that
the effect is not attributable to the surface activity alone; but it is
considered that the effect is attributable not to the hydrophobic groups
randomly distributed in the polymer chain but to the hydrophobic groups at
the terminal. In other words, PVA having a hydrophobic group at one
terminal improves the film forming properties of the sizing agent and
permits the sizing agent to form film having good physical properties.
This is because such PVA is composed of a terminal hydrophobic group and a
hydrophilic PVA moiety. This structure produces surface activity and the
PVA moiety itself has good film forming properties. In addition, the
terminal-modified PVA is compatible with ordinary PVA, anion-modified PVA,
cation-modified PVA, and other modified PVA
The adhesion to fibers of terminal-modified PVA(B) is as good as that of
ordinary PVA and other modified PVA.
Therefore, the sizing agent containing terminal-modified PVA (B) produces
outstanding weavability when used for high-quality textiles and high-speed
looms.
The sizing agent composed of (A) starch, (B) terminal-modified PVA (C)PVA,
and (D)oil for textile sizing may be incorporated with acrylic sizing
agent, carboxymethylcellulose, antifoam, and other additives without any
problem.
As mentioned above, the textile sizing agent containing (B)
terminal-modified PVA exhibits outstanding weavability when used for
high-quality textiles and high-speed looms. Needless to say, it also
exhibits outstanding weavability when used for other textiles and looms.
The textile sizing agent of the invention is formed by adding (B)
terminal-modified PVA to a sizing agent containing (A) starch,(C)PVA, and
(D)oil for textile sizing. The component(B) improves the compatibility of
(A) starch and (C) PVA and also improves the emulsification and dispersion
of (D) oil for textile sizing. Therefore, the sizing agent solution is
stable and easy to handle. Moreover,(B)terminal-modified PVA improves the
compatibility of the entire sizing agent. The sizing agent solution, upon
drying, forms uniform film having high strength and elongation. The thus
formed film improves abrasive resistance and reduces yarn-hairiness. For
this reason, the textile sizing agent of the invention is effective for
high-quality textiles and high-speed looms such as air jet loom.
The invention is now described in more detail with reference to the
following examples, which should not be construed to restrict the scope of
the invention. Quantities in the examples are based on weight, unless
otherwise indicated.
In the following examples, the viscosity of the aqueous solutions was
measured using a Brookfield viscometer.
The terminal-modified PVA(B) was prepared according to a process as
explained in Referential Example that follows.
REFERENTIAL EXAMPLE
In a reaction vessel were placed 960 parts of vinyl acetate (abbreviated as
VAc hereinafter), 230 parts of methanol, and 0.99 parts of
n-dodecylmercaptan (abbreviated as n-DDM hereinafter). The air in the
reaction vessel was completely replaced with nitrogen, and the external
temperature was raised to 65.degree. C. When the internal temperature
reached 60.degree. C., there was added 10 parts of methanol containing
0.174 parts of 2,2-azobisisobutyronitrile. Immediately thereafter, there
was added 60 parts of 80% VAc solution in methanol containing 15.3 parts
of n-DDM uniformly over 5 hours. Conversion to polymer after 5 hours was
48.2%. After 5 hours, the reaction vessel was cooled and the residual VAc
was removed under reduced pressure while adding methanol. Thus there was
obtained a 72% polyvinyl acetate (PVAc) solution in methanol. A portion of
the solution was saponified with a methanol solution of NaOH at 40.degree.
C., while keeping the PVAc conc. at 50% and the molar ratio of [NaOH] to
[VAc] at 0.1. There was obtained polyvinyl alcohol(PVA) having a degree of
saponification of 99.2%. It had a degree of polymerizati (P) of 82 as
calculated according to Nakajima equation (1) described below from [.eta.]
measured in an acetone solution at 30 .degree. c.
[.eta.]=7.50.times.10.sup.-4 .times.(P).sup.0.64 (1)
Table 2 below shows the characteristic properties of various kinds of
terminal-modified PVA (B) used in the example that follow.
TABLE 2
______________________________________
Degree of Degree of
Terminal long-
polymer- saponi-
Code chain alkyl group
ization fication
Comonomer
______________________________________
P-1 C.sub.4 H.sub.9 --
100 99.0 None
P-2 C.sub.12 H.sub.25 --
100 99.0 None
P-3 C.sub.12 H.sub.25 --
500 99.2 None
P-4 C.sub.12 H.sub.25 --
1700 88.5 None
P-5 C.sub.18 H.sub.37 --
100 76.5 Itaconic
acid 4 mol %
P-6 C.sub.12 H.sub.25 --
500 88.5 None
P-7 C.sub.8 H.sub.17 --
100 99.0 None
P-8 C.sub.8 H.sub.17 --
500 80.6 None
P-9 C.sub.3 H.sub.7 --
100 99.0 None
P-10 C.sub.18 H.sub.37 --
100 99.0 None
P-11 C.sub.22 H.sub.45 --
100 99.0 Maleic
anhydride
3 mol %
______________________________________
EXAMPLE 1
A mixture of terminal-modified PVA (P-2) and corn starch was heated and
dissolved in an autoclave at 125.degree. C. for 1 hour to give an aqueous
solution containing 5% solids. The viscosity of the solution was measured
at 20.degree. C immediately after preparation and one week after
preparation. The state of the solution was observed one week after
preparation. The same experiment as above was carried out except that P-2
was replaced by P-6.
For comparison, a solution of corn starch alone was prepared (in
Comparative Experiment 2) and a solution of corn starch and PVA ("Kuraray
Poval PVA-105") having a degree of polymerization of 550 and a degree of
saponification of 98.5 mol % was prepared (in Comparative Experiment 1)
and the viscosity of the solutions was measured in the same manner as
above. The results are shown in Table 3.
It is noted from Table 3 that the solution containing PVA-105 greatly
changes in viscosity with time and is subject to phase separation. The
solution containing corn starch alone is liable to gel soon after
preparation. By contrast, the solution containing terminal-modified PVA
changes only a little in viscosity with time and is stable even after
standing.
TABLE 3
__________________________________________________________________________
Viscosity (20.degree. C., cp)
Composition (%)
Immediately
One week
State
Experi-
Kind of Corn-
after after after
ment No.
PVA PVA starch
dissolution
dissolution
one week
__________________________________________________________________________
Experiment 1
P-2 10 90 51 61 good*
30 70 65 70 good
70 30 1280 1350 good
Experiment 2
P-6 10 90 7.5 8.0 good
30 70 15.5 16.0 good
70 30 170 175 good
Comparative
PVA-105
10 90 5.8 9.0 poor**
Experiment 1
30 70 7.6 155 poor
70 30 130 160 poor
Comparative
-- -- 100 630 gelled
gelled
Experiment 2
__________________________________________________________________________
*stable without phase separation;
**phase separation
EXAMPLE 2
A 50:50 mixture (by weight) of corn starch and terminal-modified PVA of
different type was heated in water at 95.degree. c for 2 hours to give a
5% aqueous solution. , The viscosity of the aqueous solution was measured
at 20.degree. C. immediately after dissolution and two days after
dissolution.
For comparison, aqueous solutions were prepared in the same manner as
above, except that the terminal-modified PVA wa replaced by PVA ("Kuraray
Poval PVA-117") having a degree of polymerization of 1750 and a degree of
saponification of 98.5 mol % (in Comparative Experiment 3), long-chain
alkyl group-modified PVA (PVA-L) formed by copolymerizing with 0.6 mol %
of lauryl vinyl ether, having a degree of polymerization of 700 and a
degree of saponification of 98.6 mol % (in Comparative Experiment 4), PVA
(PVA-V) f | | |
