JPS59145230A - Production of highly water-swellable vulcanized rubber product - Google Patents

Abstract

PURPOSE:To obtain a vulcanized rubber product which can show a high rate of water swelling and a high degree of water swelling even at a low content of a highly water-absorptive polymer, by adding a highly water-absorptive polymer and a filler containing a specified amount of clay. CONSTITUTION:In producing a water-swellable rubber product by adding a highly water-absorptive polymer to an ethylene/alpha-olefin copolymer or an ethylene/alpha- olefin/nonconjugated diene copolymer; a filler system containing clay in an amount of at least 60wt%, based on the total weight of carbon black and/or a white filler is added. Clays are classified into bentonite of montmorillonite group and other clays typified by kaolin group, and particularly preferred clays which can be used in this rubber product are the latter clays typified by kaolin group because of their good water swellability. Examples of the highly water-absorptive polymers used include saponified ethylene/vinyl ester/acrylate ester copolymers and crosslinked acrylic acid/acrylate salt copolymers.

Description

Detailed Description of the Invention The present invention relates to an ethylene-α-olefin copolymer or an ethylene-α-olefin-nonconjugated diene copolymer (hereinafter referred to as α-
This invention relates to a method for producing water-swellable vulcanized rubber products using propylene, which is the most representative and important olefin, and these copolymers are called ethylene propylene rubber (hereinafter abbreviated as EPR). More specifically, the present invention relates to a method of manufacturing vulcanized rubber products having improved water swelling properties.

Regarding water-swellable vulcanized rubber products using F and PR, JP-A-56-83082 and JP-A-57-119972 are known. However, in these known methods, the water swelling rate is extremely slow and the water swelling rate is also extremely low, and the volume increase when left in water for one week is approximately the same as the amount of filler. Despite this, it was at a low level of less than 100% at best. Therefore, its practical use is extremely limited.

The present inventors have conducted intensive studies on a method for drastically improving the water-swelling performance of water-swellable vulcanized rubber products using EPR, and have arrived at the present invention. Specifically, even if less superabsorbent polymer is used than in conventional methods, the water swelling rate is very fast, and the water swelling sidewheel is also very large, with an increase in volume of more than 100%, sometimes more than 800%. This also made it possible to obtain a salary.

The invention of the present inventors not only discovered a filler system with dramatically superior water swelling performance, but also achieved further improvement in water swelling performance by using EPR having specific structural and characteristic values. It is also significant in that it has improved 17 times.

EPR that can obtain extremely excellent water swelling performance as shown in the Examples below, for example, high swelling performance of around 100% after being left in water for one day and 300% or more after being left in water for 3 days.
Until now, there have been no reports of any vulcanized rubber products used. It goes without saying that for EPR, which does not have a hydrophilic group, the achievement of the present invention will greatly expand the practical application and applications of water-swellable vulcanized rubber products using EPR.

“The first feature of the present invention is the use of clay as a filler used in the production of vulcanized rubber.

Various types of carbon black, talc, clay, silica, calcium carbonate, and the like are widely used as fillers in the production of vulcanized rubber products. However, as a result of extensive studies, the present inventors discovered that in order to obtain the high swelling performance as referred to in the present invention, the filler system must be carefully selected, and the present invention was achieved. That is, clay is most suitable as a filler, and even if other fillers such as carbon black and talc are used in combination as necessary, the content of clay should be at least 60% by weight, preferably at least 60% by weight based on the total amount of fillers. It has been found that 75% by weight or more is required.

When the content of clay is low, the water swelling ability decreases by 5 degrees, requiring a large amount of water-absorbing polymer, and the water swelling ability is still significantly lower than when the clay content is 560% by weight or more. lowest).

Clays include montmorinite-based bentonite and other clays, mainly kaolin-based clays. Since bentonite swells significantly with water to form a highly viscous gel, it is widely used as a dispersant, thickener, etc. in Latte Sox Industries, etc. However, the latter's direction, which is centered on the Orin system, is more important than the Kinei Akibanko 6) Teban.
The special number is preferred because it provides good water swelling properties.

In the production of water-swellable vulcanized comb products in the present invention, fillers, process oils,
The amount of various processing aids, pigments, and anti-aging agents is small, and the amount of process oil is increased (stagnant water swelling performance is improved.Water swelling performance is improved by adding and increasing the amount of surfactants, etc. as necessary) be done.

The present invention relates to a method for producing a vulcanized rubber having high water swelling property, and the vulcanization system used is a sulfur vulcanization system consisting of sulfur and a vulcanization accelerator selected as necessary, and a sulfur vulcanization system consisting of peroxide and a vulcanization accelerator selected as necessary. Peroxide vulcanization systems, other quinoid vulcanization systems, and resin vulcanization systems, especially sulfur vulcanization systems, have excellent physical properties, and the vulcanization time can be adjusted depending on the selection and variables of the vulcanization accelerator. This is the most practical method in that it can be adjusted to a large extent.

The present inventors used this most practical sulfur vulcanization system to
As a result of studying PR's water-swellable vulcanized rubber,
It has been found that certain EPRs have extremely good water swelling properties. EPR is divided into ethylene-α-olefin copolymer and ethylene-α-olefin-nonconjugated diene copolymer. Both can be subjected to peroxaneto vulcanization. However, it can be used only for sulfur-vulcanized ethylene-α-olefin-nonconjugated diene copolymer (hereinafter abbreviated as EPDM). This EPD
The present inventors have discovered that the water swelling properties of sulfur-vulcanized rubber products using M are greatly influenced by the M of the nonconjugated diene. α in case of peroxide vulcanization
If the content, molecular weight, composition distribution, etc. of the olefin (i.e., the most typical propylene) are the same, the ethylene-α-olefin copolymer and EPD are the same.
M shows almost the same water swelling properties, and when compared in EPDM, the effect of the difference in the amount of non-conjugated diene is extremely small. On the other hand, in the case of sulfur vulcanization, it has been found that the amount of nonconjugated diene in EPDM greatly influences the water swelling properties. That is, according to the studies of the present inventors, in order to obtain high water swelling properties in a sulfur vulcanization system, the amount of non-conjugated diene in EPDM needs to be 15 or less in terms of iodine value, preferably 12 or less. I understand. EPDM with an iodine value higher than this limit value is E with a lower iodine value within this limit value.
Compared to PDM, the water swelling rate is slower and the degree of water swelling is also lower.
Therefore, its use as a water-swellable rubber product is quite limited.

The present inventors further investigated ultra-high water swelling rubber products. The ultra-high water swelling property as used by the present inventors refers to water swelling property such that the volumetric swelling rate is generally 500% or more.

The present inventors have discovered that in order to obtain such ultra-high water swelling rubber products, it is necessary to use a specific EPR.
7. In other words, the strength of EPR raw rubber itself is JISK-6
Breaking strength: 8 when measured with 801 standard JIS-9 dumbbell at 20°C and tensile speed of 500 wm/min
It has been found that it is necessary to use an EPR that has a Kg[/cr1 or more and an elongation at break of 500% or more. If EPR is outside such a limited range, ultra-high water swelling properties cannot be obtained, and even if a volumetric swelling rate of 500% or more is obtained, cracks may occur on the surface of the vulcanizate, making it difficult to put it into practical use. It is not possible. This limitation is important and useful as the iodine value of EPDM becomes lower.The Mooney viscosity of raw rubber, ML 1+4100℃, is 100 or more. The EPR is used to measure the strength of green comb by adding extender oil to bring the Mooney viscosity to 60-80.

As mentioned earlier, EPR as used in the present invention means an ethylene-α-olefin copolymer or an ethylene-α-olefin-nonconjugated diene copolymer. This is because propylene is the most common and important α-olefin;
Examples thereof include -butene, 1-hexene, 1-denitone, 4-methifle-1-pentene, and 1-heptene. Examples of non-conjugated dienes include 1,4-hexadiene, dicyclopentadiene, ethylidene, and the like. Ethylene: from 0:10 to 20:80, particularly preferably 75: by weight of the α-olefin.

25 to 40:60, and non-conjugated diene l has an iodine value of 0 to 50. Generally, 0 to 25 is used, but as mentioned above, for sulfur-cured water-swellable vulcanized rubber, the iodine value is 5. 12 or less is preferable because it is especially hot. In the present invention, other rubbers such as natural rubber, styrene-butadiene rubber, butyl rubber, chloroprene rubber, etc. can also be used in combination with EPR.

The superabsorbent polymer used in the present invention is ethylene-
Saponified product of vinyl ester-acrylic acid ester, cross-linked product of acrylic acid-acrylic acid salt copolymer, cross-linked product of alkali metal salt of starch-acrylic acid graft polymer, polyvinifle alcohol and maleic anhydride Examples include alkali salts of the reactants. EPR has heat resistance, weather resistance,
As superabsorbent polymers having excellent ozone resistance and other properties, saponified products of ethylene-viniflester-acrylic acid ester and cross-linked products of ac-11 acid-acrylic acid salt copolymers are particularly preferred. In the examples, ethylene-
This is also the reason for the use of Skageru O (manufactured by Sumima Kagaku Kogyo Co., Ltd.), which is a saponified product of vinyl ester acrylic ester.

The present invention can be used to manufacture wipers, gaskets, backings, glass runs, and various other sealing materials, building materials, and the like.

Examples using the present invention are shown below, but the present invention is not limited thereto.

Example I A blend of 80 parts by weight of filler, 5 parts by weight of zinc white, 1 part by weight of stearic acid, 80 parts by weight of Sumica gel, and 10 parts of surfactant per 100 parts of E l' R100 was prepared using Bp-type Banbury. After getting it, add tuxinol ■B Z /T
T/'f RA/M (Vulcanization accelerator manufactured by Susumu Kagaku Kogyo Co., Ltd.)
210.5/0.5/1 part by weight, sulfur 0.7
5 parts by weight were added in a roll and vulcanized at 160°C for 10 minutes to obtain a vulcanized sheet with a thickness of 2 mm. Samples with a diameter of 86 mm were punched out from the vulcanized sheet, left in water at room temperature for one week, and the swelling characteristics were measured as volume increase rate (%). However, the EPR used is ML-! +4100℃==45, propylene content 5Qw
t%, ENB type iodine value 8 EPDM.

*Comparative Example This example shows that among fillers, clay, especially kaolin clay, has the best water swelling properties.

Example 2 The results of examining the effects of the amounts of sumica gel and paraffin oil, which are super absorbent polymers, are shown. Add the above additives, use kaolin clay silkworm as filler, 160℃
Same as Example 1 except that vulcanization was performed for 7 minutes.

It is clear that it is preferable to use clay in a proportion of % or more.

Example 4 An example of the results of examining the water swelling properties of various EPRs using kaolin clay as a filler will be shown.

Vulcanizing agent: sulfur vulcanizing system, peroxide vulcanizing system 16
Vulcanization at 0°C
Qwt% 11) Measurement of volume increasing car after being left in water at room temperature for 8 days This example uses EP with an iodine value exceeding 15 in the case of sulfur vulcanization
It can be seen that R is large and the water swelling property is poor. These F,
In order to improve the water swelling properties of PR, a large amount of super absorbent polymer is required, which greatly increases the cost of rubber products.

In order to obtain a rubber product having excellent water swelling properties with a small amount of superabsorbent polymer using sulfur vulcanization, it is particularly preferable to use EPR with an iodine value of 15 or less, generally 12 or less.

Example 5 An example of evaluating the water swelling rate of the rubber product of the present invention is shown.

Blend EPR100 (parts by weight) Clay 80 Paraffin oil 0 or 80 ε Kagel
30 Surfactant 10 Zinc white 5 Stearic acid 1 Tsuxinol BZ 2, 'I'
T O,5,,TRA
0.5〃M1 Sulfur 0.75 EPR, iodine value 8, ENB type, Ml,, l+4100℃=50, vulcanization=160℃ 7 minutes vulcanization.

Water swelling speed: A sample with a diameter of 36 mm and a thickness of 2 screws was left in water and the volume increase was measured.This example shows that the swelling speed of water-swellable rubber products obtained using the present invention is very fast. . It was previously thought that an EPR vulcanized rubber product having high water swelling properties and high speed swelling properties as shown in this example could not be obtained at all.

Example 6 Although it has conventionally been difficult to obtain a vulcanized rubber having a water swelling property of 800%, the results of an investigation into a method for obtaining a vulcanized rubber having an ultra-high water swelling property of 500% or more are shown below.

Clay 150 Sumikagel 80 Surfactant 20 Zinc white 5 Stearic acid 1 Tsuxinol BZ 2 TT 0.5 TRA Q, 5 M 1 Sulfur 0.3 Vulcanization 160°C 7 minutes Vulcanization Other test methods, etc. Same as Example 1 In order to obtain a vulcanized rubber with ultra-high water swelling of 500% or more, it is necessary that the raw rubber has both high breaking strength and high breaking elongation. If either one of them is large, the shape retention after water swelling or cracks will occur on the surface, which will limit its practical use.

Continuation of page 1 0 shots by Seishi Watanabe Takatsuki Kata Umehara 2-40 Sumitomo Chemical Within Gakkogyo Co., Ltd. 0 shots Akira Masato Ogura Became a resident of 5-1 Sokai-cho, Niihama City Within Gakkogyo Co., Ltd.

Claims (1)

[Claims] l) When producing a water-swellable rubber product by adding a super absorbent polymer to an ethylene-αf olefin copolymer or an ethylene-α olefin-nonconjugated diene copolymer, carbon black and/or A process for producing a vulcanized rubber product with improved water swelling properties, characterized by adding a filler system containing at least 60% by weight of clay based on the total amount of white filler. 2) Obtain a water-swellable rubber product by sulfur vulcanization using an ethylene-α-olefin% conjugated diene copolymer in which the amount of non-conjugated diene is 15 or less in terms of iodine value.Claim 1
Method for manufacturing vulcanized rubber products as described in Section 1. 3) Claim 1 which uses an ethylene-α olefin copolymer or a conjugated diene copolymer (t is ethylene-α olefin) having a breaking strength of f3Kfl/- or more and a breaking elongation of 500% or more. Or the method for producing a vulcanized rubber product according to item 2.