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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to sanitary rubber compositions or articles having
excellent chemical and physical properties and more particularly, it is
concerned with a sanitary rubber composition or article comprising a
rubber blended with a finely divided polyethylene powder of a super-high
molecular weight. By the sanitary rubber composition or article, we mean
rubber articles in contact with foods, rubber closures or plugs for
pharmaceutical vessels, rubber products attached to medical instruments,
rubber articles used for human bodies and animals and the like, which have
some influences upon human bodies and animals directly or indirectly and
which are different from industrial rubber articles, tires and foot wears
in chemical and physical properties. That is to say, the sanitary rubber
article of the present invention includes rubber articles for foods,
drugs, cosmetics, veterinary medicines, feeds and radiation protection,
which comes under the administration of the Food and Drug Administration.
2. Description of the Prior Art
For rubber closures for drugs, for example, about 30 examination and test
items must be satisfied. These items include provisions for solving
problems such as the following: (1) if an additive used as an essential
component for a synthetic rubber is released from the surface of a
product, it becomes added to a medical fluid as fine particles, (2) when a
rubber closure of a vial is pierced by an injection needle, rubber pieces
are broken off and added to a medical fluid and (3) if an opening is
formed when the injection needle pierces the rubber closure, a medical
fluid may issue and spoil clothes. Thus, sanitary rubber articles must be
prepared so as to satisfy these newly added requirements.
Up to the present time, it has been proposed to add low molecular weight
polyethlene to various rubbers (Japanese Patent Publication No. 5973/1960,
Canadian Pat. No. 846831/1962) and to produce a rubber plug for an
injection fluid by blending a natural rubber or synthetic rubber with a
fine powder of polyethylene (Japanese Patent Publication No. 8789/1970).
In these techniques, however, a fine powder of polyethlene should be used
in a proportion of 1 to 10% by weight with carbon black and lithopone
(ZnS+BaSO.sub.4) as a reinforcing agent, since the bridging efficiency is
low and the physical properties of a bridged product are inferior.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a sanitary rubber
composition or article capable of satisfying the quality standard.
It is another object of the present invention to provide a rubber closure
for an injection, having excellent chemical and physical properties.
It is a further object of the present invention to provide a rubber
composition for a sanitary article, containing no inorganic filler or
reinforcing agent.
These objects can be attained by a rubber composition for a sanitary
article comprising a synthetic rubber and a fine powder of polyethylene
with a mean molecular weight of 1,000,000 to 1,000,000,000.
DETAILED DESCRIPTION OF THE INVENTION
The inventor has made various efforts over a long time and consequently,
has found that a sanitary rubber article which can favorably be compared
with rubber articles of the prior art using ordinary additives is obtained
by mixing a synthetic rubber prepared by solution polymerization with a
fine powder of polyethylene having a mean molecular weight of
1.times.10.sup.6 to 1.times.10.sup.9, bridging with a bridging agent and
forming.
Accordingly, the present invention provides a rubber composition for a
sanitary article, comprising a synthetic rubber, particularly prepared by
solution polymerization, and a finely divided powder of polyethylene
having a mean molecular weight of 1.times.10.sup.6 to 1.times.10.sup.9
(hereinafter referred to as HMWPE) and a sanitary rubber article such as
rubber closure for an injection fluid, comprising a blend of a synthetic
rubber and HMWPE, which has been bridged and shaped.
That is to say, in the present invention, sanitary rubber articles, for
example, rubber closures for injectable products such as wads, plugs with
or without a skirt or flange and caps, having excellent physical
properties (tensile strength, elongation, etc.) and sanitary properties
(KMnO.sub.4 consumption, ultraviolet absorption spectrum, etc. of the
extraction solution) can be obtained by adding only HMWPE to a synthetic
rubber prepared by solution polymerization, followed by bridging and
shaping. Generally, HMWPE is added in a proportion of 3 to 50 parts by
weight to 100 parts by weight of a synthetic rubber.
However, because there are a number of kinds of sanitary rubber products
and a number of requirements to be satisfied, addition of only HMWPE is
sometimes insufficient. In such cases, other additives such as silicon
oxide, aluminum silicates, magnesium silicates, clays and titanium oxides
can be added in a proportion of 1 to 30 parts by weight to 100 parts by
weight of a synthetic rubber for the purpose of improving the abrasion
resistance, flexibility resistance and compression set. If the addition
exceeds 30 parts by weight, the bridged rubber product is not suitable as
a sanitary rubber article because of increase of the KMnO.sub.4
consumption and residue on evaporation of the extraction solution.
When the quantity of HMWPE is more than 50 parts by weight, the bridged
rubber product is not suitable as a sanitary rubber article because of the
higher hardness, the resinous properties in the quantity of strain and
degree of crystallization and the lower visoelasticity at a high
temperature. HMWPE is a polyethlene, for example, prepared by polymerizing
ethylene gas at a pressure of 0 to 7 atm in the presence of a Ziegler
catalyst consisting of triethylaluminum and carbon tetrachloride in
combination and the mean molecular weight is at least 1.times.10.sup.6 as
determined by the viscosity method or at least 3.times.10.sup.6 as
determined by the light scattering method, while an ordinary polyethlene
(referred to as PE) has a molecular weight of 2-10.times.10.sup.4 as
determined by the viscosity method or 6-30 .times.10.sup.4 as determined
by the light scattering method.
Comparison of the properties of HMWPE and PE is tabulated below:
______________________________________
Properties HMWPE PE Test Method
______________________________________
Density (g/cc)
0.93-0.94 0.92-0.94 ASTM D 1505
Tensile Strength at
400-440 90-170 ASTM D 638
Breaking Point
(kg/cm.sup.2)
Elongation at
350-400 150-750 ASTM D 638
Breaking Point
Melting Point(.degree.C.)
136 105-118 ASTM D 2117
Vicat Softening
134 76-115 ASTM D 1525
Point (.degree.C.)
Thermal Deformation
85 -- ASTM D 648
Temperature (.degree.C.)
______________________________________
Preparation of a finely divided powder of HMWPE is carried out by
mechanically crushing pellets of high molecular weight polyethylene in the
air or water, by dissolving it in a hot solvent such as carbon
tetrachloride or trichloroethylene and then cooling rapidly or mixing it
with water or alcohol to precipitate it in the form of fine particles.
Preferably, HMWPE having a particle size small enough to pass through a
sieve of 74.mu. (200 mesh) is used, but the presence of large amounts of
fine particles of less than 1.mu. is not desirable since scattering takes
place due to electrification and dispersion in the rubber is prevented.
When small samples of HMWPE are viewed under an electron microscope, a
number of cracks can be seen on the surfaces of the particles and a number
of heteromorphic particles can be seen. Therefore, it is assumed that a
synthetic rubber and HMWPE form a polymer network and thus HMWPE gives
more excellent sanitary products than PE in respect of improving the
abrasion resistance, impact strength, heat and deformation resistance,
chemical and solvent resistance and safety property. In the present
invention, accordingly, a sanitary rubber product can be produced without
using inorganic reinforcing agents or fillers such as aluminum silicate,
magnesium silicate and barium sulfate, and vulcanizing agents.
As the synthetic rubber of the present invention, the rubbers used can be
prepared by solution polymerization, for example, isobutylene-isoprene
rubber (IIR), chlorinated isobutylene-isoprene rubber (CIIR), brominated
isobutylene-isoprene (BIIR), isobutylene-isoprene-divinylbenzene
copolymer, ethylene-propylene rubber (EPM), ethylene-propylene-diene
rubber (EPDM), chlorosulfonated polyethylene (CSM), epichlorohydrin rubber
(CO, ECO, GCO, GECO), butadiene rubber (BR), isoprene rubber (IR),
styrene-butadiene rubber (SBR), isoprene-styrene rubber (SIR) and
ethylene-vinyl acetate copolymer (EAM). These rubbers can be used
individually or in combination. Thermoplastic rubbers of styrene-butadiene
or styrene-isoprene can also be used. Synthetic rubbers by emulsion
polymerization and natural rubbers are not suitable for sanitary rubber
articles due to the presence of emulsifiers and proteins, respectively.
Organic peroxides, which can be used as a vulcanizing agent in the present
invention, are for example dicumyl peroxide,
1,4-di-(t-butylperoxyisopropyl)benzene,
2,5-dimethyl-2,5-di-(t-butylperoxy)hexane,
2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3 and the like.
In addition, as another bridging agent, there are sulfur- or
organosulfur-imparting vulcanizing agents and as a bridging aid, there are
vulcanization accelarating agents, vulcanization activating agents,
processing aids, vulcanization retarding agents and the like, typical of
which are zinc white, stearic acid, magnesium oxide, tetramethyl-thiuram
disulfide, tetraethylthiuram disulfide, dipentamethylene tetasulfide, zinc
di-n-butyl-dithiocarba-mate, zinc diethyldithiocarbamate,
N-cyclohexyl-2-benzo-thiazolylsulfenamide,
N-t-butyl-2-benzothiazolyl-sulfenamide, tetramethylthiuram monosulfide,
fatty acid esters and fluorine-containing lubricants. These agents are
generally added in a proportion of 0.05 to 10 parts by weight to 100 parts
by weight of a synthetic rubber.
Furthermore, organosilane compounds such as vinyltriethoxysilane,
vinyltriacetylsilane, vinyl-tris (.beta.-methoxyethoxy)silane,
.gamma.-methacryloxypropyltrimethoxysilane,
.gamma.-glycidoxypropyltrimethoxysilane, RTV silicone rubbers, silicone
oils and the like can also be added in a proportion of 0.05 to 3 parts by
weight to 100 parts by weight of a synthetic rubber.
The rubber composition of the present invention can be subjected to
radiation vulcanization, for example, by the use of an electron beam.
As the sanitary rubber product or article of the present invention, for
example, there are given rubber parts for rice cookers, sealants for water
bottles or cans, rubber closures for vials of medicines or chemicals and
medical devices such as parts of artificial kidneys, syringes, etc.
The following examples are given in order to illustrate the present
invention in detail without limiting the same.
EXAMPLES
HMWPE (Hizex Million 240 M -commercial name-manufactured by Mitsui Sekiyu
Kagaku Kogyo KK. molecular weight =200.times.10.sup.4 as determined by
viscosity method, grain size =capable of passing through a sieve of
105.mu., melting point =136.degree. C.) was added to IIR (JSR Butyl
365-commercial name-, unsaturation degree =2.0 mol %, ML.sub.1+4
(100.degree. C.)=45) in proportions as shown in Table 1, mixed at a
temperature of 80.degree. to 120.degree. C. in a pressure kneader (made by
Moriyama Seisakujo KK), compounded with bridging systems as shown in Table
1 in a biaxial rubber roll according to ASTM D 3188 ('73) and then
subjected to a test using an oscillating disk rheometer (hereinafter
referred to as ODR) (made by Toyo Seiki Seisakujo KK) according to ASTM
D-2705 ('67), thus obtaining results as shown in Table 2.
TABLE 1
______________________________________
Examples Comparative Examples
Components 1 2 3 4 3 2 1
______________________________________
IIR: JSR 365
100 100 100 100 100 100 100
HMWPE 43 20.5 5.3
Polyethylene.sup.1 5.3 20.5 43
Zinc Oxide 2 2 2 2 2 2 2
Stearic Acid
0.5 0.5 0.5 0.5 0.5 0.5 0.5
Sulfur 1 1 1 1 1 1 1
Vulcanization
Accelerator TRA.sup.2
0.4 0.4 0.4 0.4 0.4 0.4 0.4
BZ.sup.3 0.7 0.7 0.7 0.7 0.7 0.7 0.7
______________________________________
Note:
.sup.1 FLOTHENE UF commercial name manufactured by Seitetsu Kagaku KK,
grain size = capable of passing through a sieve of ASTM No. 80, melting
point = 103-111.degree. C., high density
.sup.2 dipentamethylene thiuram hexasulfide
.sup.3 zinc din-butyl dithiocarbamate
TABLE 2
______________________________________
ODR Test (temp 160.degree. C., amplitude angle 3.degree.)
Examples Comparative Examples
1 2 3 4 3 2 1
______________________________________
Torque (kg/cm)
Initial (a) 32.0 26.2 22.0 20.1 22.4 30.8 38.3
Minimum (b) 24.5 20.5 16.4 15.8 14.8 l2.3 11.2
Maximum (c) 48.5 44.0 38.5 36.7 33.6 27.6 22.3
(c)-(b) 24.0 23.5 22.1 20.9 18.8 15.3 11.1
Cure Time (minute)
tc (10) 2.9 2.9 2.9 2.9 2.9 3.0 3.1
tc (90) 8.6 8.7 8.9 9.9 9.8 9.9 9.9
tc (90)-(10)
5.7 5.8 6.0 7.0 6.9 6.9 6.8
______________________________________
As apparent from these results, HMWPE is capable of increasing the torque,
while PE decreases the torque, the difference increasing with the larger
the quantity of HMWPE. PE acts as a softening agent and as an agent that
hinders the vulcanization action of IIR.
TABLE 3
______________________________________
Physical Properties of Vulcanizates.sup.1
Examples Comparative Examples
1 2 3 4 3 2 1
______________________________________
Hardness (Hs)
59 45 34 30 36 59 76
300% Modulus
36 20 13 10 9 15 20
(kg/cm.sup.2)
Tensile Strength
76 76 69 76 107 118 115
(kg/cm.sup.2)
Elongation at
460 500 750 800 830 820 800
Break (%)
Permanent Set (%)
2.7 2.0 3.2 3.4 5.9 29.6 65.6
______________________________________
Note:
.sup.1 vulcanization temperature 160.degree. C. .times. 30 minutes
according to JlS K 6301 (1975)
The vulcanization was carried out according to SRIS-3603 and the test of
the vulcanizates was carried out according to JIS K-6301 (1975).
A sanitation test was carried out by extracting a sample in water at
90.degree. C. for 30 minutes and determining the residue on evaporation
and the consumption of potassium permanganate according to JIS 9010
(1982).
TABLE 4
______________________________________
Sanitation Test
Examples Comparative Examples
1 2 3 4 3 2 1
______________________________________
Residue on Evapor-
3.2 4.2 6.1 8.3 12.6 23.2 36.8
ation (ppm)
KMnO.sub.4 Reducing
4.6 5.2 6.3 7.8 9.6 12.8 15.6
Substance (ppm)
______________________________________
As apparent from the results of Tables 3 and 4, HMWPE is capable of
improving the modulus, permanent set, residue on evaporation and
consumption of KMnO.sub.4, while PE hinders the curing.
It can clearly be understood that HMWPE and PE have the similar physical
properties, but show completely different performances when added to IIR
and the like. For example, HMWPE and PE have the following physical
properties in the form of films:
______________________________________
Tensile Strength (kg/cm.sup.2)
Elongation at Break (%)
______________________________________
HMWPE 236 690
PE 206 880
______________________________________
EXAMPLE 4
Using the following composition, mixing was carried out in an analogous
manner to Examples 1-3:
TABLE 5
______________________________________
CIIR (CHLORO BUTYL 1066.sup.1)
100 parts by weight
HMWPE (HIFAX 1900.sup.2)
28
Zinc Oxide 1
Magnesium Oxide 2
Stearic Acid 0.3
Tetramethylthiuram Disulfide
0.6
Zinc Diethyldithiocarbamate
0.6
______________________________________
Note:
.sup.1 commercial name, manufactured by Exxon Chemical
.sup.2 commercial name, manuactured by Hercules, mean molecular weight as
determined by viscosity method = 700 .times. 10.sup.4, density = 0.94,
grain size = capable of passing through a sieve of ASTM No. 70, tensile
strength of film = 239 kg/cm.sup.2
Vulcanization of the compound was carried out by pressing at a temperature
of 150.degree. C. for 30 minutes according to JIS K 6301.
TABLE 6
______________________________________
Physical Properties of Vulcanizates.sup.1
______________________________________
Hardness (Hs) 38
500% Modulus (kg/cm.sup.2)
32
Tensile Strength (kg/cm.sup.2)
122
Elongation at Break (%)
760
Permanent Set (%) 3.8
______________________________________
Note:
.sup.1 temperature 150.degree. C. .times. 30 minutes according to JIS K
6301
The rubber sample was first washed with a dilute alkali (e.g. NaHCO.sub.3)
and then extracted with an amount of water 10 times the weight of the
rubber at a temperature of 121.degree. C. for 60 minutes according to the
test method of rubber closures for aqueous infusions as specified in The
Pharmacopoeia of Japan 41. The test results of the extracted liquid and
the standard values of The pharmacopoeia of Japan are shown in Table 7:
TABLE 7
______________________________________
Extraction Test
Measured
Standard
Value Value
______________________________________
Description (%) 99.5 99.0
Foam Test (min) 2 3
pH 0.8 .+-.1
Zinc (.mu.g/ml) 0.01 0.5
KMnO.sub.4 -reducing Substance (ml)
0.8 2.0
Residue on Evaporation (mg)
0.8 2.0
Ultraviolet Absorption Spectrum
0.08 0.2
______________________________________
Specificity tests were also carried out as follows:
(1) Insoluble Particulate Matter Test
10 rubber closures are placed in a hard glass bottle to which 100 ml of
dust-free water is added and which is shaked for 20 seconds, then allowed
to stand for 1 hour and subjected to measurement 4 times using a
light-shielded type automatic fine particle meter (PC-320, -commercial
name- made by HIAC/Royco Co.). The initial data is discarded and a mean
value is taken of the next three data.
(2) Determination of Fragmentation
According to British Standard 3263 (1960), water is charged in a bottle,
which is then closed by the rubber closure and fastened by an aluminum
cap. A part of the aluminum cap is removed for the ease of penetration by
an injection needle and a standard test needle with an outer diameter of
0.72 mm (22 G made by TOP) is penetrated through it 10 times. Then, the
bottle is shaken several times and the number of rubber fragments in the
water is counted.
(3) Determination of Penetrability
According to British Standard 3263 (1960), the force of penetration is
measured by the use of a Shimazu Autograph (commercial name, made by
Shimazu Seisakujo KK) when a standard test needle with an outer diameter
of 0.72 mm is passed through the central part of the rubber closure.
(4) Determination of Self-Sealability
Water is charged in a bottle of 500 ml, which is then closed by the rubber
plug, fastened by an aluminum cap, heated at 121.degree. C. for 30 minutes
and cooled. A standard test needle is allowed to penetrate "OUT" part of
the rubber closure and the bottle is allowed to stand in an inverted state
for 1 hour. Then, an air needle is allowed to penetrate through it to let
400 ml of the water out of the bottle, the test needle is withdrawn and at
the same time, the quantity of water flowing out is measured.
The results of the above described tests are shown in Table 8:
TABLE 8
______________________________________
Measured Standard
Value Value
______________________________________
Insoluble Particulate Matter Test
10 .mu.m (number) 1 10
5 .mu.m (number) 46 100
Determination of Fragmentation
no 3
Determination of Penetrability (g)
460 1000
Determination of Self-Sealability (ml)
0.5
______________________________________
It will be apparent from the results of the specificity test as shown in
Table 8 that the rubber sample satisfied all the standard requirements and
above all, showed better results in the insoluble particulate matter test
than rubber plugs produced by the prior art processes.
EXAMPLES 5 to 8
Blending was carried out according to "Test Method of Rubber", page
108-118, i.e. ASTM standard method:
TABLE 9
______________________________________
Examples
5 6 7 8
______________________________________
Rubber BIIR.sup.1
CSM.sup.2
GECO.sup.3
BIIR.sup.1
100 100 100 100
HMWPE (Example 1)
23 23 23 33
Zinc Oxide 1 -- -- 1
Magnesium Oxide
0.3 10 5 0.3
White Carbon 8 8 8 --
Silane Coupling
0.5 0.5 2 0.5
Agent.sup.4
Sulfur 0.3 0.8 -- --
TMTD.sup.5 0.2 0.8 .sup.6 1.0
.sup.7 0.6
Curing (.degree.C. .times. min)
150 .times. 20
160 .times. 30
160 .times. 30
160 .times. 20
______________________________________
Note:
.sup.1 POLYSAR BROMO BUTYL X2 commercial namemanufactured by Polysar Co.,
ML.sub.1+4 (125.degree. C.) 53, Br = 1.9 wt %
.sup.2 Hypalon commercial name manufactured by Du Pont, ML.sub.1+4
(100.degree. C.) 55, Cl = 3.5% by weight
.sup.3 Gechron 3100 commercial name manufactured by Nippon Zeon Co.,
epichlorohydrinethylene oxideallylglycidyl ether ternary compolymer
.sup.4 Mercaptopropyltrimethoxysilane
.sup.5 Tetramethylthiuram disulfide
.sup.6 2,4,6trimercapto-s-triazine
.sup.7 1,1di-(t-butylperoxy)-3,3,5-trimethylcyclohexane
TABLE 10
______________________________________
Physical Properties of Vulcanizate
Examples
5 6 7 8
______________________________________
Hardness (Hs) 38 39 41 43
Tensile Strength (kg/cm.sup.2)
106 132 112 86
Elongation at Break (%)
620 520 580 500
Compression Set* (%)
37 31 28 23
______________________________________
Note:
*press 25%, temp 70.degree. C. .times. 22 hrs, etc. according to JIS K
6301
TABLE 11
______________________________________
Extraction Test.sup.1
Examples
5 6 7 8
______________________________________
CH.sub.3 COOH 20%
Residue on Evapor-
0.1 0.1 0.3 0.1
(90.degree. C..times. 30 min)
ation (ppm)
KMnO.sub.4 -Reducing
0.3 0.2 0.5 0.3
Substance (ppm)
UV Spectrum 0.12 0.10 0.15 0.15
C.sub.2 H.sub.5 OH 20%
Residue on Evapor-
0.1 0.1 0.2 0.1
(90.degree. C. .times. 30 min)
ation (ppm)
KMnO.sub.4 -Reducing
0.2 0.2 0.4 0.2
Substances (ppm)
UV Spectrum 0.01 0.01 0.02 0.02
______________________________________
Note:
1According to the sanitation test method of rubber products of JIS T 9010
(1982)
As is evident from the results of Table 11, the rubber products of the
present invention are suitable for rubber parts for the preparation of
foods.
EXAMPLES 9 TO 10 AND COMPARATIVE EXAMPLES 5 TO 7
The procedure of blending the composition shown in Table 12 was carried out
according to ASTM D 3403.
TABLE 12
______________________________________
Examples Comparative Examples
9 10 5 6 7
______________________________________
IR (Nipol IR 2200).sup.1
100 100 100 100 100
Stearic Acid 0.3 0.3 0.3 0.3 0.3
Zinc Oxide 2 2 2 2 2
Sulfur 2 2 2 2 2
TMTS.sup.2 0.7 0.7 0.7 0.7 0.7
HMWPE.sup.3 30 15 -- -- --
PE.sup.4 -- -- -- 15
Dixie Clay -- -- -- -- 30
______________________________________
Note:
.sup.1 ML.sub.1+4 (100.degree. C.) 83, cis 98%
.sup.2 Tetramethylthiuram Monosulfide
.sup.3 Hizex Million 240M commercial name same as that of Example 1
.sup.4 FLOTHENE UF commercial name same as that of Example 1
An ODR test was carried out in an analogous manner to Example 1 except that
the temperature was adjusted to 170.degree. C. The results obtained are
shown in Table 13:
TABLE 13
______________________________________
ODR Test
Examples Comparative Examples
9 10 5 6 7
______________________________________
Torque (kg/cm)
Initial (a) 23.0 19.2 15.2 15.1 22.2
Minimum (b) 19.5 16.8 14.0 11.0 19.8
Maximum (c) 48.6 44.1 39.2 20.8 47.9
(c)-(b) 29.1 27.3 25.2 9.8 28.1
Cure Time (minute)
t'c (10) 4.8 4.8 4.6 2.4 2.4
t'c (90) 22.9 23.0 22.8 20.4 82.0
t'c(90)-t'c(10)
18.1 18.2 18.2 18.0 79.6
______________________________________
Comparative Example 5 is a standard pure rubber compound. In Examples 9 and
10 wherein HMWPE is added thereto, the maximum torque and torque (c)-(b)
are increased, which implies that extensive vulcanization networks are
formed. In Comparative Example 6, wherein PE is added, however, the
maximum torque and (c) -(b) are smaller, which implies little
vulcanization. HMWPE hardly changes the curing time (t'c (90)), but Dixie
Clay lengthens the curing time.
TABLE 14
______________________________________
Physical Properties of Vulcanizates.sup.(1)
Comparative
Examples Examples
9 10 5 6 7.sup.(3)
______________________________________
Hardness (Hs) 46 41 35 no.sup.(2)
44
300% Modulus (kg/cm.sup.2)
32 59 25 52
Tensile Strength
141 136 127 102
(kg/cm.sup.2)
Elongation at Break (%)
600 520 720 620
Tear Resistance (kg/cm)
25.3 28.2 24.5 36.2
______________________________________
Note:
.sup.(1) vulcanization condition 160.degree. C. .times. 40 minutes
.sup.(2) No vulcanization test sample was formed.
.sup.(3) vulcanization condition 180.degree. C. .times. 40 minute
In Comparative Example 6, PE was too soft to obtain a vulcanization test
piece for the measurement of physical properties. That is, this
comparative example shows that PE hinders the vulcanization. Examples 9
and 10 show that the hardness, modulus, tensile strength and tear
resistance are improved. In Comparative Example 7, Dixie Clay retards the
vulcanization to such a large extent that a test piece capable of
measuring the physical properties can only be obtained by raising the
vulcanization temperature: but the physical properties of the vulcanizate,
however, are relatively excellent.
TABLE 15
______________________________________
Hygienic Test.sup.(1)
Comparative
Examples Examples
9 10 5 6 7
______________________________________
Material Test
Pb (ppm) 0.05 0.05 0.05 no.sup.(2)
2.8
Cd (ppm) 0.01 0.01 0.01 0.1
Extraction Test.sup.(3)
Residue on Evaporation (ppm)
0.8 0.8 0.8 1.5
KMnO.sub.4 -Reducing Substance
1.0 1.0 1.8 2.8
(ppm)
Pb (ppm) 0.01 0.01 0.01 0.5
As (ppm) 0.01 0.01 0.01 0.1
Zn (ppm) 0.1 0.1 0.1 0.5
Formaldehyde ND.sup.(4)
ND ND ND
Phenol ND.sup.(4)
ND ND ND
UV Spectrum 0.08 0.10 0.10 0.28
______________________________________
Note:
.sup.(1) according to JIS T 9010
.sup.(2) No rubber test piece was obtained.
.sup.(3) extracted with water at 120.degree. C. for 30 minutes
.sup.(4) no detection
In the material test, Comparative Example 7 shows the presence of
considerable amounts of heavy metals such as Pb and Cd from the fillers
and zinc oxide, but Examples 9 and 10 show only the presence of Pb and Cd
in trace amounts. In Comparative Example 7, heavy metals such as Pb and Zn
are also found in the extracted solution. This implies that the rubber
product of Comparative Example 7 is unhygienic.
EXAMPLES 11 TO 17 AND COMPARATIVE EXAMPLES 8 AND 9
Blending of the composition shown in Table 16 was carried out according to
ASTM D 3484-76.
TABLE 16
__________________________________________________________________________
Comparative
Examples Examples
11 12 13 14 15 16 17 8 9
__________________________________________________________________________
BR.sup.(1)
100 100 85 100 100 100 100 100 100
SBR.sup.(2)
-- -- 15 -- -- -- -- -- --
HMWPE.sup.(3)
15 9 15 10 15 15 3 -- --
PE.sup.(4)
-- 6 -- -- -- -- -- 6 15
Filler.sup.(5)
-- -- -- 5 2 -- 15 15 --
Organo 0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Peroxide.sup.(6)
Other Vulcani-
-- -- -- -- -- 1.0.sup.(7)
-- 1.0 --
zing Agent
Silane Coupl-
-- -- -- -- 1 -- 0.5 -- --
ing agent.sup.(8)
__________________________________________________________________________
Note:
.sup.(1) BRO1 commercial name manufactured by JSR, ML.sub.1+4 (100.degree
C.) 44, quantity of cis 96%
.sup.(2) SL 552 commercial name manufactured by JSR, ML.sub.1+4
(100.degree. C.) 55, bonded styrene 24%, cis 1,4 content 20%
.sup.(3) Hifax commercial name manufactured by Hercules Powder Co., mean
molecular weight 300 .times. 10.sup.4 (by viscosity method)
.sup.(4) Shorex commercial name manufactured by Showa Denko KK, low
density PE, melting point 92.degree. C.
.sup.(5) Whitex commercial name manufactured by Southern Clay
.sup.(6) 1,1di-(t-butylperoxy)-3,3,5-trimethylcyclo-hexane
.sup.(7) 1,2polybutadiene
.sup.(8) Vinyltrimethoxysilane
An ODR test was carried out in an analogous manner to Example 1 except that
the temperature was adjusted to 155.degree. C. The results obtained are
shown in Table 17:
TABLE 17
______________________________________
ODR Test
Com-
parative
Examples Examples
11 12 13 14 15 16 17 8 9
______________________________________
Torque
(kg/cm.sup.2)
Initial (a)
21.5 19.5 21.6 19.8 21.2 20.5 19.8 19.5 20.0
Minimum
20.4 18.1 19.5 18.4 19.1 18.5 18.5 14.2 15.0
(b)
Maximum
50.4 51.7 50.0 56.4 54.3 55.7 51.8 44.0 42.2
(c)
(c)-(b)
30.0 33.6 30.5 38.0 35.2 37.2 33.3 29.8 27.2
Cure
Time
(minute)
t'c (10)
1.7 1.5 1.0 1.4 1.5 1.3 1.5 1.4 1.5
t'c (90)
8.9 8.0 7.4 7.9 7.8 7.7 8.2 7.4 7.9
t'c(90)-
7.2 6.5 6.0 6.5 6.3 6.4 6.7 6.0 6.4
t'c(10)
______________________________________
It is apparent from the results of Table 17 that in comparison of Example
11 and Comparative Example 9, the former is more excellent in respect of
the maximum torque and (c)-(b), which shows the difference between HMWPE
and PE. Furthermore, the use of PE (Example 12), filler (Example 14) and
silane coupling agent (Example 15) with EMWPE results in increase of the
torque value (c) -(b). Even when a part of BR is replaced by SBR (Example
13), similar results are obtained to the case when only BR is used.
TABLE 18
__________________________________________________________________________
Physical Properties of Vulcanizates.sup.(1)
Comparative
Examples Examples
11 12 13 14 15 16 17 8 9
__________________________________________________________________________
Hardness (Hs)
43 45 44 48 44 46 43 43 40
200% Modulus
18 20 15 23 21 24 19 12 10
(kg/cm.sup.2)
300% Modulus
29 31 25 33 31 35 30 23 21
(kg/cm.sup.2)
Tensile 58 60 50 60 58 58 58 43 42
Strength(kg/cm.sup.2)
Elongation at
435 430 400 410 425 400 430 390 380
Break (%)
Tear Resis-
15.9
16.3
14.9
16.5
16.5
16.0
16.0
11.5
10.2
tance (kg/cm)
__________________________________________________________________________
Note:
.sup.(1) at 140.degree. C. for 25 minutes
In comparison of Example 11 with Comparative Example 9, it can clearly be
appreciated that HMWPE gives a larger modulus, tensile strength and tear
resistance than PE. Other Properties are substantially similar to those of
the ODR test as shown in Table 17. That is, the joint use of PE (Example
12) or filler (Example 14) with HMWPE results in raising the bridging
efficiency.
TABLE 19
__________________________________________________________________________
Hygienic Test.sup.(1)
Comparative
Examples Examples
11 12 13 14 15 16 17 8 9
__________________________________________________________________________
Residue on Evaporation (ppm)
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.5
0.5
KMnO.sub.4 -Reducing
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.5
0.5
Substance (ppm)
UV Spectrum 0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.05
0.05
__________________________________________________________________________
Note:
.sup.(1) extracted at 90.degree. C. for 30 minutes according to JIS T 901
(1982)
As is evident from the test results of Table 19, the rubber products of the
present invention are satisfactory in their hygienic properties.
EXAMPLE 18 AND COMPARATIVE EXAMPLE 10
The composition of Table 20 was blended and subjected to tests in an
analogous manner to Example 11.
TABLE 20
______________________________________
Example 18
______________________________________
BR (BRO2.sup.(1)) 92 parts
EPDM (EP 25.sup.(2)) 8
White Carbon 3 3
Zinc Oxide 1 1
HMWPE (similar to Example 1)
14 14
PE (Shorex M222.sup.(3))
1 1
2,5-dimethyl-2,5-di-(t-butylperoxy)-
0.6 0.6
hexyne-3
______________________________________
Note:
.sup.(1) commercial name, manufactured by JSR, ML.sub.1+4 (100.degree. C.
44, cis 94%
.sup.(2) commercial name, manufactured by JSR, ML.sub.1+4 (100.degree. C.
90, iodine number higher
.sup.(3) commercial name, manufactured by Showa Denko KK 1ow dens1t PE
TABLE 21
______________________________________
Physical Properties of Vulcanizates.sup.(1)
______________________________________
Hardness (Hs) 41
300% Modulus (kg/cm.sup.2)
27
Tensile Strength (kg/cm.sup.2)
87
Elongation at Break (%)
530
______________________________________
Note:
.sup.(1) curing at 160.degree. C. for 40 minutes
TABLE 22
______________________________________
Material Test
______________________________________
Cd (ppm) 0.01 Atomic Absorptiometric Analysis
5
Pb (ppm) 0.05 Atomic Absorptiometric Analysis
5
______________________________________
The rubber sample was extracted with an amount of water 10 times the weight
of the rubber at 121.degree. C. for 60 minutes according to the test
method of rubber closures for aqueous infusions as specified in The
Pharmacopoeia of Japan 41. The test results of the extracted liquid and
the standard values of The Pharmacopoeia of Japan are shown in Table 23:
TABLE 23
______________________________________
Extraction Test
Measured
Value Standard Value
______________________________________
Description (%) 99.5 99.0
Foam Test (min) 2 3
pH 0.6 .+-.1.0
Zinc .mu.g/ml) 0.01 0.5
KMnO.sub.4 -reducing Substance (ml)
0.8 2.0
Residue on Evaporation (mg)
0.3 2.0
UV Absorption Spectrum
0.07 0.2
______________________________________
A specificity test was carried out in an analgous manner to that of Example
4. The results obtained are shown in Table 24:
TABLE 24
______________________________________
Measured Value
Standard Value
______________________________________
Particulate Matter Test
10 .mu.m (number)
1 10
5 .mu.m (number)
26 100
Fragmentation no 3
Penetrability 530 1000
Self-Sealability (ml)
no
______________________________________
The rubber closure of the present invention is available for injection of
grape sugar, amino acids and electrolyte drugs.
TABLE 25
______________________________________
Comparative
Example 18
Example 10
______________________________________
Rubber 92 parts.sup.(1)
92 parts.sup.(2)
EPDM.sup.(3) 8 8
White Carbon 3 3
Zinc Oxide 1 1
HMWPE.sup.(4) 14 14
PE.sup.(5) 1 1
2,5-dimethyl-2,5-di-
0.6 0.6
t-butylperoxy)-hexyne-3
______________________________________
Note:
.sup.(1) BR: JSR BRO2 commercial name manufactured by JSR, ML.sub.1+4
(100.degree. C.) 44, cis 94%
.sup.(2) SBR: JSR 1502 commercial name manufactured by JSR, ML.sub.1+4
(100.degree. C.) 52, styrene 23.5% (by cold emulsion polymerization
method)
.sup.(3) EPDM: JSR EP 25 commercial name manufactured by JSR, ML.sub.1+4
(100.degree. C.) 90 iodine number higher
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