JP2876697B2 - Rubber composition for sponge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sponge having particularly good skin, whitening of the surface,
The present invention relates to a sponge rubber composition which is free from bloom and bleed and has excellent settability and processability.

[Prior Art] Sponge rubber is used in automobiles and building materials for the purpose of weight reduction.

Among these, especially for sponge rubber for automobiles, recently, there is a particularly high demand for improvement of sponge skin, which is one of the sensitivity qualities. There is also a strong need for improvement in appearance quality such as whitening, absence of bloom and bleed, and long-term sealing performance, that is, low set resistance.

In general, sponge rubber having good skin is obtained by highly filling a filler such as carbon black or heavy carbon, improving the extruded skin with an extruder, and achieving a good balance between vulcanization and foaming.

In order to prevent whitening, bloom and bleeding, the types and amounts of vulcanizing agents and vulcanization accelerators used have been devised, the types of process oils have been selected, and white carbon and polyethylene glycol have been added. In addition, in order to obtain a sponge rubber having low settling, means such as use of a high molecular weight polymer or soft carbon having a large particle size, selection of the type and amount of a vulcanizing agent and a vulcanization accelerator, and improvement of a degree of crosslinking are required. Has been taken.

[Problems to be Solved by the Invention] However, balancing vulcanization and foaming of sponge rubber is a very difficult technique, and the foaming state is also affected by humidity and the like, so that sponge rubber with good skin is provided. It is currently difficult to obtain.

Even if the type and amount of the compounding agents are devised to prevent whitening, blooming and bleeding, there are problems such as being effective in one formulation but not effective in another formulation, and there is no definitive prevention method at present. Was. In addition, even if various splinters are obtained by blending and devising low spatter, problems such as processing problems, imbalance between vulcanization and foaming, and problems such as roughening of the skin occur, resulting in satisfactory satisfaction. No sponge rubber was obtained.

An object of the present invention is to provide a rubber composition for a sponge which has particularly good skin, does not have whitening, bloom and bleed on the surface of the sponge, and has excellent settling and workability. .

[Means for solving the problem] As a result of various studies, the present inventors have found that by blending 5 to 100 parts by weight of a lightweight black filler (pulverized coal) with 100 parts by weight of rubber and a foaming agent, These goals have been achieved.

As the rubber used in the present invention, usually, ethylene-α- having excellent weather resistance and ozone resistance used in the rubber industry.
Olefin-non-conjugated diene copolymer rubber, ethylene-α-
Olefin-copolymer rubber, chloroprene rubber, NBR / PVC
In addition to blended rubber, NBR / EPDM blended rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, chlorinated ethylene-propylene rubber, silicone rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, natural rubber, etc. can be used. . Among them, the above rubber having excellent weather resistance is preferable, and furthermore, ethylene-
α-olefin-non-conjugated diene copolymer rubber and / or ethylene-α-olefin copolymer rubber are more preferred. Further, a small amount of polyethylene, polypropylene, phenol resin, silicone resin, fluorine resin, or the like may be blended with rubber.

Examples of the ethylene-α-olefin copolymer rubber include an ethylene-propylene copolymer rubber and an ethylene-butene-1 copolymer rubber, and an ethylene-propylene copolymer rubber is preferable. Examples of the non-conjugated diene of the ethylene-α-olefin-non-conjugated diene copolymer rubber include ethylidene norbornene, dicyclopentadiene, and 1,4-hexadiene.

The lightweight black filler used in the present invention is a powder obtained by pulverizing coal, and has a preferable average particle diameter of 20.
μm or less, more preferably 1 to 10 μm, particularly preferably about 7 μm. The preferred specific gravity range is 1.
It is 1 to 1.3. As a specific gravity measurement method, JIS R-722
Measure according to 2. Particularly preferred lightweight black fillers include a specific gravity of about 1.22, an average particle diameter of about 7 μm, and a pH of about
7.0 black filler. For example, United States, KEYSTONE FlLL
ER & MFG.CO. mineral black.

The amount of the lightweight black filler is 5 to 100 parts by weight, preferably 10 to 80 parts by weight, more preferably 20 to 60 parts by weight based on 100 parts by weight of the rubber having excellent weather resistance. If the amount is less than 5 parts by weight, the effects of the present invention cannot be exhibited. If the amount is more than 100 parts by weight, problems such as processability and edge breakage during extrusion occur.

In the present invention, it is of course possible to use a lightweight black filler, ordinary carbon black and a white filler in combination.

The rubber composition for a sponge of the present invention contains a foaming agent. Specific examples of the foaming agent include nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, azo compounds such as azodicarbonamide, and sulfonylhydrazide compounds such as toluenesulfonylhydrazide. In addition, two or more foaming agents can be used, and various foaming assistants can be used in combination as needed. The foaming agent is 1-1 for 100 parts by weight of rubber.
0 parts by weight, preferably 2 to 6 parts by weight can be used.

The rubber composition for sponge of the present invention, in addition to rubber and lightweight black filler and foaming agent, reinforcing agent, filler, softener,
Processing aids, hygroscopic agents, zinc white, stearic acid, vulcanizing agents, cross-linking agents, vulcanization accelerators and the like can be added.

Specific examples of the reinforcing agent and the filler include carbon black such as furnace black, channel black, and thermal black, white carbon, calcium carbonate, talc, clay, high styrene resin, coumarone, and indene resin.

Specific examples of the softener include process oil, lubricating oil,
Petroleum softeners or plasticizers such as liquid paraffin can be exemplified.

Still other additives include molding aids, pigments,
Acid acceptors and other conventional additives can be mentioned.
If an ordinary sulfur vulcanization or LCM device is used, vulcanization and foaming with an organic peroxide is also possible.

Further, as a method of producing the rubber composition for sponge of the present invention, for example, a usual rubber kneading machine, that is, kneading with a Banbury mixer, oven rolls and the like, then molding, usually HAV, UHF, LCM, PCM, etc. Can be produced by continuous vulcanization. Further, it can also be manufactured by transfer molding or injection molding.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples as long as the gist is not exceeded.

All parts in the following Examples and Comparative Examples are by weight.

Example 1 Production and evaluation of a sponge rubber composition were performed as follows.

Production method EPDM of Table 1, below, after kneading the compounding agent up to the processing aid with a 20 l Banbury mixer, the remaining compounding agent was added with a 14 inch roll, and extruded at 70 ° C with a φ75 mm extruder, Next, continuous vulcanization and foaming were performed in a 220 ° C. HAV line with a residence time of about 5 minutes.

Extrusion die shape: Outside diameter φ15m at the center upper part of ribbon of thickness 1.5mm, width 17mm
m, with integrated tube of inner diameter φ12mm.

Evaluation method Processability The compound was visually evaluated based on the state of the compound (collection) after being discharged from the Banbury mixer and the state of winding around a roll, and the results were indicated as good (○), acceptable (△), and poor (×).

 The specific gravity was measured by the flotation method.

Surface skin Judged visually. (X) is poor surface skin, (○)
Indicates that the skin had good surface texture, and (◎) indicates that the skin was even better.

Compression set (hereinafter abbreviated as CS) Using a test piece obtained by the above method, a spacer (t ₂ ) is used so that the compressibility is 50% of the original height (t ₀ ) of the test piece.
Is attached and is kept at 70 ° C. for a predetermined time. After a lapse of a predetermined time (described in Table 2), the test piece was released, cooled at room temperature for 30 minutes, and then the height (t ₁ ) of the test piece was measured.

CS (%) = _{[(t 0 -t 1) / (} t 0 -t 2) ] × left at room temperature for the resulting sponge at 100 surface fouling the method was visually evaluated contaminating after 14 days.

 Table 2 shows the results of the above evaluations.

Example 2 A sponge rubber composition was produced and evaluated in exactly the same manner as in Example 1, except that 60 parts by weight of the lightweight black filler was used instead of 30 parts by weight, and no white filler was used. Was. The evaluation results are shown in Table-2.

Comparative Example 1 A sponge rubber composition was produced and evaluated in exactly the same manner as in Example 1, except that the lightweight black filler was not used, and the white filler was used in place of 30 parts by weight and 60 parts by weight. Was. The evaluation results are shown in Table-2.

Comparative Example 2 A sponge rubber composition was produced and evaluated in exactly the same manner as in Example 2, except that 130 parts by weight of the lightweight black filler was used instead of 60 parts by weight. The evaluation results are shown in Table-2.

As can be seen from Table 2, the rubber composition for a sponge of the present invention has no problem in processability, is excellent in settability, and more surprisingly, has particularly good surface skin and non-staining property on the surface. Was also excellent. On the other hand, in Comparative Example 1 in which the lightweight black filler was not blended, the surface skin,
There was a problem in surface contamination. Also in Comparative Example 2 in which the amount of the lightweight black filler was too large, there were problems in workability and surface texture.

[Effect of the Invention] By compounding a rubber with a lightweight black filler and a foaming agent, surprisingly, the surface skin is particularly good, and further, there is no contamination such as whitening of the surface, bloom, and bleed due to a compound such as zinc. A rubber composition for a sponge having excellent properties and processability can be obtained.

The sponge rubber composition of the present invention includes a door seal sponge for a white automobile, a trunk seal sponge,
It can be suitably used for various sponge products such as sponge rubber for building materials.

Claims (1)

(57) [Claims] 1. A rubber composition for a sponge, comprising 5 to 100 parts by weight of a lightweight black filler and a foaming agent, based on 100 parts by weight of rubber.