JPS6279232A - Cushioning base material - Google Patents

Abstract

PURPOSE:To obtain a cushioning base material having excellent body-pressure distributing property and durability, by compounding a rubber base with a highly water-absorbing polymer and a crosslinking agent, crosslinking the resultant water-absorbing rubber composition and swelling the crosslinked composition with water to a specific volume dilation ratio. CONSTITUTION:A rubber base [preferably an ethylene-alpha-olefin(-conjugated diene) copolymer having a breaking strength of >=8kgf/cm<2> and a breaking elongation of >=500%] is compounded with a highly water-absorbing polymer (preferably saponified ethylene-vinyl ester-acrylate polymer) and a crosslinking agent (preferably a sulfur crosslinking agent). The objective cushioning base material can be produced by crosslinking the obtained water-absorbing rubber composition (preferably to an extent to get a 300% stress of 5kgf/cm<2>) and swelling with water to a volume dilation ratio of >=3, times preferably 3-15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cushion base material obtained by swelling with water a water absorbent rubber composition comprising a rubber base material and a super absorbent polymer. More specifically, the present invention relates to a cushion base material having specific mechanical properties and water swelling properties, excellent body pressure dispersibility, and durability.

Conventionally, urethane foam, natural rubber latex foam, various natural or synthetic fibers, etc. are used as cushion base materials, and silane products are known. In addition, Kui Thin products, which have the best body pressure dispersion properties, which is a particularly important property for cushions, are known for water mats, water beds, etc., and are made from water as a cushioning material, making them suitable for people with physical disabilities, illnesses, etc. It is used for people who use Cushilon products for long periods of time.

Cushion products that use water as a cushioning material have excellent body pressure dispersion properties, but when you move your body, it shakes a lot, which is the same phenomenon as seasickness experienced when riding a ship sailing in rough seas. This is known to cause seasickness in users.

For this reason, cushion products that use a gel-like material as a cushion base material have been developed and are being used as cushioning products that come in contact with water. However, this cushion product has a disadvantage in that it has poor body pressure dispersion properties compared to cushion products based on water.

In order to improve body pressure dispersion even a little, it is necessary to make the thickness thicker, but this has the problem of making the weight heavier.Also, even if the thickness is increased, the body pressure dispersion The characteristics are still insufficient, and improvements have been desired, especially among physically disabled people, sick people, and people who sit for long periods of time (for example, drivers of trucks, buses, trains, etc.).

The present invention provides a new, durable base material that meets these needs. The present invention will be explained in detail below.

The present invention is a cushion in which the volume of a water-absorbing rubber composition made from rubber as a raw material and blended with a super absorbent polymer and a cross-linking agent is increased by three times or more by a water-swelling treatment after cross-linking. It is related to the base material. The rubber used as a raw material here is not particularly limited, but includes ethylene-α olefin co-ffi rubber, ethylene-α olefin-nonconjugated diene terpolymer rubber (hereinafter the above two are referred to as ethylene rubber), styrene- Butadiene rubber (SB
R), acrylonitrile-butadiene rubber (NBR),
Examples include isobutylene-isoprene rubber (IIR), butadiene rubber (BR), acrylic rubber (ACM), chloroprene rubber (CR), various thermoplastic elastomers, and natural rubber (NR).

Among these, ethylene rubber is particularly preferably used because it is excellent in water resistance, bacteria resistance, cold resistance, and fillability with fillers.

Examples of α-olefins used in ethylene rubber include propylene, 1-butene, 1-hex-1-pentene, and 4-methyl-1-hexene, with propylene and 1-butene being particularly representative. It is.

Further, examples of the non-conjugated diene include 1,4-hexadiene, dicyclopentadiene, and ethylidene norbornene.

Here, the weight ratio of ethylene/α-olefin in the ethylene rubber is 90/10 to 20/80, preferably 75
/25 to 40/60. The non-conjugated diene has an iodine number of O to 50. Generally, bases equivalent to 0 to 25 are used.

On the other hand, the superabsorbent polymers used in the present invention include saponified products of ethylene-vinyl ester-acrylic acid ester, cross-linked products of acrylic acid-acrylate copolymers, saponified products of starch-acrylonitrile graft polymers, Examples include a crosslinked product of an alkali metal salt of a starch-acrylic acid graft polymer, an alkali salt of a reaction product of polyvinyl alcohol and maleic anhydride, and in particular, a saponified product of ethylene-vinyl ester-acrylic ester, an acrylic acid- Crosslinked acrylate copolymers are particularly preferred because they have excellent water swelling properties.

The crosslinking agent includes a sulfur crosslinking agent consisting of sulfur and a vulcanization accelerator selected as necessary, a peroxide crosslinking agent consisting of peroxide and a crosslinking aid selected as necessary,
Examples include quinoid crosslinking agents and mamine crosslinking agents, but sulfur crosslinking agents are particularly useful in that they have excellent physical properties and can be widely controlled in temperature and time of crosslinking treatment by selecting and varying the vulcanization accelerator. It is.

In the present invention, in addition to rubber, super absorbent polymer, and crosslinking agent, inorganic fillers such as carbon black, talc, clay, calcium carbonate, and silica, process oil, blowing agent, blowing aid, aging Inhibitors, processing aids, pigments, and rust inhibitors can be used in combination.

Among them, carbon black, Shiroko-+011, and process oil are preferably used because they act as adding strength to the cushion base material, as fillers to reduce costs, or as compounding agents that give a soft feel.

These raw materials are mixed using a Banbury mixer, kneader, roll, or the like. The rubber composition thus obtained is crosslinked using a press, autoclave, injection, oven, continuous crosslinking device, or the like.

Generally, crosslinking treatment is carried out by heating at a temperature of 100° C. to 250° C. for several minutes to several hours.

The water swelling treatment is carried out by immersing the crosslinked molded article in water. The water temperature is usually room temperature, but sometimes heated water is used, and the immersion time is not particularly limited, but it is preferred that a high water swelling ratio can be achieved in a practically short time.

These conditions are selected so that the volume of the molded article increases by at least 8 times its original volume upon water immersion. The greater the increase in volume due to water swelling treatment, the better the desired characteristics of the cushion such as body pressure dispersion, but if the increase in volume is too large, durability will decrease and seasickness will be more likely to occur. For this reason, it is desirable to increase the volume by about 3 to 15 times.

In order to quickly increase the sowing volume through water swelling treatment, we select a super absorbent polymer with excellent water swelling properties.
It is preferable to increase the amount. It is preferable that the filler selected and added as necessary has a high supporting property, and clay is particularly preferable since it also has reinforcing properties. Because carbon black and talc are hydrophobic, they are often used in combination with hydrophilic fillers.

Processing oils have the great effect of imparting flexibility to crosslinked rubber and thereby improving water swelling properties, and are therefore used with great care. The addition of surfactants is also effective in increasing the rate of water swelling.

As mentioned above, in the present invention, a water swelling treatment is performed to obtain a large volume increase in order to improve the chewability of the cushion such as body pressure dispersion. It has been found that in order for the cushion base material not to be destroyed even with such a large increase in volume, it is necessary to use a rubber that has both high breaking strength and high breaking elongation.

This point is particularly important when it is necessary to increase the swelling ratio.For example, when ethylene propylene rubber is used as one raw material rubber, the breaking strength is 8 f/cj or more and the breaking elongation is 500%. Excellent effects can be obtained when the above conditions are met. When a rubber with low breaking strength and breaking elongation is used, cracks (breakage cracks) occur in the cushion base material after water swelling treatment, which is not preferable from the viewpoint of durability.

In addition, the breaking strength and breaking elongation referred to here are for JI with a thickness of 2 cm.
2 using a dumbbell-shaped test piece No. S K-63018.
Measured at 0°C and tensile speed of 500 m/min.

In the present invention, the various rubbers mentioned above can be used alone or in combination as the rubber base material.

Ethylene rubber is exemplified as a rubber particularly preferably used in the present invention, but other rubbers may be used for cost reduction, etc.
For example, natural rubber, styrene-butadiene rubber, etc. can be used in combination.

High water absorbency 1 wound molecule is 10 per 100 melon parts of raw rubber base material
~300 parts by weight, preferably 20 to 150 parts by weight are used. However, if a filler is used in Odori, more than 300 parts may be used.

As mentioned above, sulfur crosslinking agents are the most common and important crosslinking agents. The amount of sulfur used is 10% of the raw rubber base material.
0.05-10il per 0 parts! Parts are used.

``m-+m=processing 1-1-1-1 times higher rate--11 times higher rate--required-'--in one case--is -0,-
It is preferable to "use" F ~ -5 weight 4 = 'S-, and an improvement in durability is desired.For A1, the amount of E.O.W. 17 l, A=♂=Gokunshire-p When obtaining a high volume increase through swelling treatment, 0.1 to 5 parts by weight is preferable, and improves durability. When this is desired, it is common to increase the amount of sulfur.

In addition, the compounding agent used as needed is Alkahone Flak, and the white filler is O~ per 1 part of 100 weight of raw rubber.
100 parts, often in the range of 50 to 600 parts, and process oils are also used in θ to 100 parts, often in the range of 10 to 600 parts, and carbon black and white fillers are used. The larger the amount of surfactant used, the more it is used.
It is preferable to use a larger amount of carbon black and white filler, but the upper limit is sometimes limited due to bleeding problems.

Using a foaming agent or foaming aid to make a crosslinked product into a foam is a good idea! i Rapid water swelling, temperature water swelling, product increase water swelling,
Preferred from the viewpoint of silane tactility.

According to the method of the present invention, when the strength and elongation of the rubber material is sufficiently high, it is made into a foam, and the amount of the blowing agent and foaming aid used is 1 to 50! parts, preferably 8-20f
Lffi section is used.

In the method of the present invention, a rubber composition as described above is subjected to a crosslinking treatment. The main purpose of the crosslinking treatment is to prevent the occurrence of breakage cracks due to the large volume increase caused by the water-wetting treatment and to impart durability to the water-swollen rubber cushion base material. In order to achieve life, it is necessary to
The 18 dishes are important crafts.

Cross-linked rubber has excellent physical properties and water swelling properties, but in order to obtain excellent cushioning properties and a soft feel, it is necessary to
% elongation stress is preferably 10 to 4 f/cd or less, preferably 5 f/cd or less, 3
As the 00% elongation stress increases, the water swelling property tends to decrease, while at the same swelling degree, the material feels hard and the body pressure dispersion property deteriorates. In addition, the lateral sliding property, which indicates the ability of the cushion base material to follow the movement of the body, also deteriorates.

The cushion base material using the low-stress crosslinked rubber of the present invention has excellent properties as described above, and provides a cushion particularly suitable for physically disabled or sick people who cannot move their bodies freely. These people especially need a cushion that does not block blood circulation.

In the present invention, ethylene rubber with particularly high breaking strength and breaking elongation is used for the cushion base material with low elongation stress, and a relatively large amount of process oil and a small amount of crosslinked ril are used.
A method such as shortening the crosslinking treatment using 1 is adopted.

When manufacturing a desired cushion product, the shape and dimensions of the crosslinked rubber molded product are determined by taking into account the volume increase due to water swelling treatment in addition to the required shape and dimensions of the product. If necessary, they may also be made with ridged or wavy patterns, holes made, or a portion cut out to fit the human body. Moreover, it is also possible to use one cut into a chive shape or a tanzak shape.

The crosslinked rubber is immersed in water or water containing necessary additives and subjected to water swelling treatment to become a cression base material.

The obtained clision base material is a film of polyethylene, polyvinyl chloride, ethylene vinyl acetate polymer, etc.
Composite with exterior materials such as cloth and leather. In the production of Cushion products, urethane foam, rubber foam, cotton, etc. are also used in combination as auxiliary cression base materials. Depending on the cosmetic product, a method is also adopted in which the treated rubber is placed inside the exterior body and then water is injected into it to perform water swelling treatment before use.

The present invention will be explained below with reference to Examples, but these are merely illustrative and the present invention is not limited thereto.

Examples 1 to 4, Comparative Example 1.2 The results of examining the water swelling properties of each of the Kashi ethylene rubbers are shown in Table 1 as reference examples.

\, \, ゝ-1 ゛\ Out 2) Use a kneader for crosslinking (3) Crosslinking conditions 160℃ - 20 minutes Press crosslinking (4)
Water Swelling 41 Conditions A test piece measuring 40 m x 40 cm x 5 beaks was left in water at room temperature for a certain number of days.

(6) Sumikagel ■520 Super absorbent polymer manufactured by Sumitomo Chemical Co., Ltd. According to the present examples and comparative examples, ethylene propylene rubber with high breaking strength and elongation at break was used to obtain a high volume magnification of 5 times or more. I found out that I needed to.

When using a rubber with a small breaking strength and a small elongation at break like E to improve workability, use a rubber with a large breaking strength and a large elongation at break like C in combination as in Example 4 to improve the strength and processability. You can balance your sexuality.

In order to obtain a good swelling ratio as a water-swellable rubber, it is desirable that the raw material rubber has a breaking strength of 111 fΔ or more and a breaking elongation of 500% or more.

Examples 5 to 8, Comparative Example 8 (1) Crosslinking and Water Swelling Treatment Results of crosslinking conditions, crosslinked rubber properties, and water swelling properties are shown in Tables 2 and 8ffl Physical properties of ethylene propylene rubber F Mooney viscosity ML1+4 10
0°C near 5ENB type Iodine ffJ: 24 Breaking strength: 5.6V4f/d Breaking elongation = 560% (2) Kneader used for kneading (3) Crosslinking conditions Examples 5, 6.8 Press crosslinking at 160°C for 1o.

Example 7 12 (1-12 minutes press cross-linking foaming Comparative example 8 100°C-10 minutes press cross-linking The sample was left in a 0.2% by weight aqueous solution of butyl at room temperature until it was approximately 60+m square.

(2) Flexibility ◎: Excellent, Q: Good, △: Fair (3) Hardness 5RIS 0101 Based on C type hardness tester.

(4) Elongation stress was measured using a No. 2 dumbbell according to JIS K2SO3.

Two specimens each measuring 150 square meters x 15 square meters by 5 m were taken from the sheet and left in an aqueous solution of 0.2 ii [%] of butyl paraoxybenzoate at room temperature until they reached approximately 80 square meters.

(Characteristics of cushion obtained from water-swollen rubber sheet Approximately 8o obtained by blending, crosslinking, and water-swelling treatment in Examples 5, 6.7, and Comparative Example 8).

■Measure the hardness of the water-swellable rubber sheets at the corners, then wrap them in two layers with a 50μ thick polyethylene film, heat seal, and then wrap them with a 200μ thick polyvinyl chloride film and heat-seal them using high-frequency welding. The water-swellable rubber sheet was sealed to obtain a cushion material.

Evaluation of Cushion Material Using the obtained cushion material, its kutsushiran properties were evaluated.

The Kutsushiran properties are comprised of four items: compression properties, repeated compression durability, lateral sliding properties, and body pressure dispersion properties, and the methods are as follows.

■ Compression characteristics and repeated compression durability test Using an electro-hydraulic fatigue vibration tester, 4Kr up to a load of tooKf using a 200mm diameter pressure plate.
Pressure was applied at a pressure rate of /see, and the amount of strain at a constant load was determined from the recorded SS curve.

Next is the load! 60 between 10 ooh and 1 oohO I met.

■ Lateral sliding test The amount of brick movement was measured.

■ Body pressure distribution measurement test The pressure distribution applied to the test material was measured when the tester sat down.

These results are shown in Table 4. In addition, as Comparative Example 4, a commercially available Kusshi carbon material made of a gel-like substance manufactured by American Emi Co., Ltd. was used for comparison.

As is clear from Table #14, the cushion material of Comparative Example 8, which was not crosslinked, had poor repeated compression durability and could not be put to practical use. .

The cushion materials of Examples 6, 6 and 7 exhibited excellent properties.

Furthermore, these cushioning materials were thinner and lighter than commercially available cushioning materials made of gel-like substances, but had comparable or superior properties. That is, in terms of body pressure dispersion characteristics, pressure dispersion is good and maximum pressure is reduced for people whose body type tends to concentrate pressure on the ischial bones and underground bones, such as tester B who has a body type. Among those in Example 8, cross-linked products such as those in Examples 6 and 6 with a low 800% elongation stress of 54 f/- or less had a better balance in all the cushion properties including lateral sliding properties. It had excellent properties.

Claims (4)

[Claims] (1) After crosslinking a water absorbent rubber composition made by blending a superabsorbent polymer and a crosslinking agent into a rubber base material, body pressure dispersion is achieved by increasing the volume by three times or more through water swelling treatment. Cushion base material with excellent strength and durability. (2) The cushion base material according to claim 1, which is crosslinked so that the 300% elongation stress is 5 Kgf/cm^3 or less. (3) The cushion base material according to claim 1, characterized in that a rubber base material having a breaking strength of 8 Kgf/cm^3 or more and a breaking elongation of 500% or more is used. (4) The cushioning group according to claim 1 or 3, wherein the rubber base material is an ethylene-α-olefin copolymer and/or an ethylene-α-olefin-nonconjugated diene copolymer. Material.