JPS59142238A - Uncrosslinked water-swellable rubber composition - Google Patents

Abstract

PURPOSE:The titled rubber composition excellent in water swellability and shape retention, containing an ethylene/alpha-olefin (nonconjugated diene) copolymer having breaking chracteristic and an elongation at break, each of which is higher than a specified value, and a highly water-absorptive polymer. CONSTITUTION:An ethylene/alpha-olefin/nonconjugated diene copolymer having a breaking strength >=8kgf/cm<2> and an elongation at break >=500% is produced by copolymerizing ethylene with an alpha-olefin (e.g., propylene) and, optionally, a nonconjugated diene (e.g., 1,4-hexadiene) by using empirically selected conditions of polymerization catalyst, polymerization temperature, polymerization time, etc. This copolymer is mixed with a highly water-absorptive polymer (e.g., saponified ethylene/vinyl ester/acrylate ester copolymer) to obtain the purpose uncrosslinked water-swellable rubber composition.

Description

Detailed Description of the Invention The present invention relates to ethylene-α-olefin copolymers or ethylene-α-olefin-nonconjugated diene copolymers (propylene is the most representative and important α-olefin, so these copolymers The present invention relates to a water-swellable rubber composition using ethylene propylene rubber (hereinafter referred to as ethylene propylene rubber, abbreviated as EPR). More specifically, the present invention relates to a non-crosslinked water-swellable rubber composition using E1) R having limited properties.

Water-swellable rubber products such as sealants are known, but most of the rubber base materials used are mainly urethane, and non-crosslinked water-swellable rubber products using EPR are unknown. . EPR has superior properties in many properties, such as heat resistance, weather resistance, ozone resistance, and water resistance, compared to urethane and the like. In particular, excellent water resistance is a desirable point for water-swellable rubber products. The present inventors have been studying water-swellable comb products using EPR having these excellent properties for many years. As a result, the more a formulation is adopted that improves water swelling performance and water swelling rate, for example, the more the amount of superabsorbent polymer used, the more the rubber elasticity after water swelling is lost, and the shape It was found that there was a serious problem in that the retention capacity decreased, sealing performance etc. decreased, and the desired property of water swelling could not be utilized. As will be shown as a comparative example in the Examples below, in extreme cases, the rubber product may be completely dispersed in water and may not retain its original shape. The inventors have endeavored to solve this problem in detail,
This invention is a result of the present invention, and makes it possible to produce water-swellable non-crosslinked rubber products that are excellent in both shape retention and water-swellability.

The present invention relates to rubber compositions containing highly defined EPR and water-absorbing polymer molecules.

In the present invention, the limited EPR means that the breaking strength of the EP rubber itself, that is, the EPR raw rubber is 8 ・kq f /
crl or more, preferably LOkQf/cr1 or more, and elongation at break of 500% or more. It is characterized by very large breaking strength and breaking elongation, and if only one of them is large, it is not possible to simultaneously achieve both high water swelling performance and excellent shape retention. A non-crosslinked water-swellable rubber product with such defined polymer properties is completely unknown, and the present invention is of great significance. The invention will be described in further detail below.

EPR as used in the present invention is abbreviated from propylene, which is the most representative and important α-olefin, but there are also 1 other α-olefins.
-butene, 1-hexene, ■-den, 4-methyl-1-pentene, 1
-heptene, 4-methyl-1-hexene and the like. Examples of non-conjugated dienes to be copolymerized if necessary include 1,4-hexadiene, dicyclopentadiene, and ethylidene norbornene. Ethylene: α71-
L/fin weight ratio is 90:10 to 20:80
, particularly preferably from 75:25 to 40:60.

The non-conjugated diene has an iodine value of O to 50, generally 0 to 25. Although EP) I- as referred to in the present invention has high breaking strength and elongation,
This EPR is controlled by empirically selecting or setting the polymerization catalyst, polymerization temperature, polymerization time, etc.

The EPR of the present invention has a thickness of 2 #1I (7) JIS K-
No. 68013 dumbbell-shaped raw rubber was selected by measuring its breaking strength and elongation at a tensile rate of 5 Q Q mg/min at 20°C. However, the Mooney viscosity of raw rubber is MLJ 10tFl 00 'CT: 100
JaJ's second one is ML1+ by adding extender oil.
After adjusting the temperature to 4100° C. to 50° to 8°, measurements are taken.

The superabsorbent polymer used in the present invention is ethylene-
vinyl ester-acrylic acid ester crosslinked product, acrylic acid-acrylate copolymer crosslinked product, starch-acrylonitrile graft polymer saponified product, starch
Crosslinked product of alkali metal salt of acrylic acid graft polymer,
Examples include an alkali salt of a reaction product of polyvinyl alcohol and maleic acid. Since EPR has excellent heat resistance, weather resistance, ozone resistance, etc., superabsorbent polymers also have these properties and ethylene has excellent water swelling performance.
Particularly preferred are saponified products of vinyl varnish-through acrylic esters and crosslinked products of acrylic acid-acrylate copolymers.

Although the rubber composition of the present invention contains limited EPR,
As the rubber base material, natural rubber, other types of synthetic rubber such as 5BI (, CR, NBR, etc.), or EPR outside the limited range may be used in combination.A rubber composition using EPR and other rubber in combination is the rubber composition of the present invention. (This applies.

The superabsorbent polymer is used in an amount of 0.11 parts by weight or more, generally less than 100 parts by weight, per 100 parts by weight of the rubber base material.

The greater the amount used, the greater the water swelling performance and the greater the water swelling rate. In the rubber composition of the present invention, a filler is used as necessary as described below, but the water swelling performance and water swelling rate vary greatly depending on the packaging and composition of the filler. Generally, the more filler is used, the more superabsorbent polymer is used. When a filler is used in an amount of 100 parts by weight per 100 parts by weight of the rubber base material, a superabsorbent polymer having an amount of 5 parts by weight or more is usually used.

The rubber composition of the present invention contains fillers, processing oils, processing aids, pigments, etc., as necessary.

Examples of the filler include various types of carbon black, talc, clay, calcium carbonate, and silica, but the most important one is clay, which has excellent water swelling properties. Multiple fillers may be used if necessary.

Although the composition of the present invention does not necessarily require a water-soluble surfactant, since the water swelling rate is greatly improved, it is often 0.1% per 100 car weight parts of the rubber base material.
-100 vehicle parts, preferably 1 to 80 parts are used.

The composition of the present invention has excellent properties in both water swelling performance and shape retention. In general, the larger the water swelling, the more difficult it is to maintain the shape, so the composition of the present invention exhibits excellent characteristics in the volume swelling range of 50% or more, particularly in high volume swelling chain acids of 200% or more.

It should be noted that shape retention as used in the present invention refers to the improvement of the basic shape before and after swelling with water, and does not necessarily determine the shape of the composition of the present invention. That is, the composition of the present invention may be used as a so-called molded product, which is formed into a ribbon shape or a rod shape using an extruder, or a sheet shape using a calendar roll, or it may be used as a so-called molded product, such as a putty. It is sometimes available in cans or tubes.

Some examples are shown below, but the present invention is not intended to collect electricity.It should be noted that a saponified product of ethylene-vinyl ester-acrylic ester is used as the super-absorbent 4 molecule; This is because water-absorbing polymers are preferable in terms of water-absorbing performance compared to other water-absorbing polymers.

Example 1 The water swelling characteristics of each ENB type EPR with different breaking strength and breaking elongation of raw rubber are shown.

(Composition) EPk*1 100 (Heavy plan) Clay 200 Paraffin oil
100 Sumikagel *2 40 Surfactant 10 Li Oil-extended sample contains Extended oil *2 Ethylene-vinyl ester-acrylic acid ester saponified product (kneading) Using kneader (Water swelling property measuring method) 36 Combinations Using a sample with a thickness of 2 mm, it was left in water for a certain period of time, the volume before and after swelling with water was measured, and the shape retention ability was evaluated.

EXAMPLE The test results of the water swelling 4''8 characteristics of various DCPD type EPRs are shown below.The test conditions such as formulation are the same as in Example 1.

As is clear from Examples 1 and 2, in order to have both excellent water swelling performance and shape retention, EPR, which is superior to raw rubber in terms of breaking strength and breaking elongation, should be selected. Must have. It can be seen that only a high breaking strength results in poor water swelling performance, and only a large breaking elongation results in poor shape retention after water swelling.

Example 8 The characteristics of a rubber composition of the present invention using E i' R in combination with other rubbers having excellent breaking strength and elongation at break are shown.

The formulation etc. are the same as in Example 1. (However, EPR is the total amount of EPR and other rubbers in the compounding system.) Shape retention ○: Good □ ×: The shape collapses when taken out of water.

XX: The shape is so deformed that it no longer retains its original shape when left in water.

Example 4 The water swelling properties of the composition of the present invention using various fillers are shown.

(Composition) EP-Al 65 ('
14g PEPR-A5 70 Filler 150 Paraffin oil 50 Sumikagel 50 Surfactant 15 (Ii l) 11tx ], , kr, 5 is the same as in Example 1) (mixed purity) BR32 Banbury, bulk injection 10 Mixing (method for measuring water swelling properties) 4
A 5 m long sample extruded with 2x201 ribbon ties using a 5-length extruder was used for one cycle.

2 times after 5 days of niJ left in water The volume increase was determined.

Both have good shape retention Clay is particularly preferred as a filler. I understand.

Claims (1)

[Claims] The breaking strength is 8 kqf/cd or more, and the breaking elongation is 5.
00% or more of ethylene-α-olefin copolymer or ethylene-α-olefin-nonconjugated diene copolymer and superabsorbent polymer. Crosslinked water-swellable rubber composition