JPS61284411A - Manufacture of sponge product - Google Patents

Abstract

PURPOSE:To obtain a sponge product whose surface skin is excellent, foaming is high and specific gravity is low, by method wherein vulcanization and the foaming are performed after electron-ray irradiation of a molded material of a sponge compounding composite of ethylene-alpha olefin-dicyclopentadiene for its main ingredient. CONSTITUTION:As for rubber and various kinds of materials, a necessary quantity of the same are kneaded by making use of a kneading machine and made into a sponge compounding composite. Electron-ray irradiation treatment is applied to a sponge compounding composite after the same has been processed by making use of a calender roll and extruding machine and formed into an unvulcanized molded material. Accelerating voltage and irradiation dose are decided as irradiation terms; when a suitable range is shown as an example, 100kv-500kv and 1Mrad-20Mrad are used respectively as the accelerating voltage and irradiation does. Vulcanization and foaming are applied to the molded material to which electron-ray irradiation treatment has been applied, through a hot air vulcanizing tank, UHF vulcanizing tank, and fluidized bed vulcanizing tank or vulcanizing can, and the same is completed as a sponge product having a purposed improved surface skin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a sponge product made of ethylene-α olefin rubber having an improved surface texture.

More specifically, a molded article of a sponge composition of ethylene-α-olefin rubber containing ethylene-α-olefin-dicyclopentadiene rubber as a main component is subjected to electron beam irradiation treatment, followed by vulcanization and foaming. The ethylene-alpha olefin rubber represented by ethylene-propylene-nonconjugated diene copolymer has excellent weather resistance, heat resistance, ozone resistance, etc. It is widely used in various sponge products such as sponges, sealing sponges, vibration-proofing and sound-proofing sponges, etc. By the way, such sponge products are generally made by processing an uncrosslinked rubber composition containing a foaming agent and a crosslinking agent using an extruder, 1/Production by creating a rectangular shape by preforming using a press, etc., and then crosslinking and foaming it in a heating tank such as a hot air tank, fluidized bed tank, high frequency heating tank, or steam tank. has been done. Here, foaming generally progresses by thermal decomposition of the foaming agent, but if crosslinking and foaming precede too much, problems will occur such as a rough surface due to air bubbles being removed, and only a product with a low foaming ratio can be obtained. Therefore, when producing sponge products, a high vulcanization rate is usually required to match the decomposition rate of the blowing agent. Fast vulcanizing rubbers such as rubber are often used, and relatively slow vulcanizing rubbers such as ethylene-α olefin di-V chlorpentadiene rubber are used as supplementary materials. The amount of ethylene-α olefin-dicyclopentadiene rubber used in combination is 40% based on the entire ethylene-α olefin-nonconjugated diene rubber.
When manufacturing sponge products using the conventional vulcanization process, ethylene-alpha olefin-dicyclopentadiene rubber is used in amounts less than 1%, generally in the range of 10 to 80% by weight. In this case, it was not possible to obtain a highly foamed, low specific gravity sponge product with a good sponge skin.

However, it has been said that it is impossible to manufacture sponges using this manufacturing method using ethylene-α-olefin-dicyclopentadiene rubber alone.
The present inventors have exploited these excellent characteristics of the ethylene-α-olefin-dicyclobentadiene comb, which has the major characteristics of being economical and having excellent storage stability for sponge compositions compared to rubber. Taking advantage of this, we have conducted extensive research into a method for producing highly foamed, low-density sponge that is highly economical, has good thermal stability during processing and storage stability of the composition, and has an excellent surface texture for sponge products, and has developed the present invention. This is what I got.

The method of the present invention involves applying an electron beam irradiation treatment to a molded product of a sponge compound composition containing ethylene-α-olefin-dicyclopentadiene rubber as a main component, and then heat-treating the molded product. This is a method of manufacturing sponge products with improved surface texture by sulfurization and foaming.The difference from conventional methods is that only the surface layer is crosslinked using electron beams prior to vulcanization and foaming. After a smooth crosslinked layer is formed on the surface layer of the rubber molded product by electron beam crosslinking, vulcanization and foaming of the inner layer progresses, resulting in a good surface texture. It is believed that a sponge with a high expansion ratio can be obtained.

In the present invention, ethylene-α-olefin rubber containing ethylene-α-olefin-synchropentadiene rubber as a main component, exemplified tf, ethylene-α-olefin-V-clopentadiene rubber up to at least 8096 ioo*, Preferably, it is an ethylene-α olefin-non-[E'ene rubber mixture containing 6096 or more and up to 100%. Although there is no particular limitation on the component with zero residue, for example, ethylene-α olefin, which has a relatively high vulcanization rate,
α-olefin-ethylidene rubber is preferable. As used in the present invention, α-olefins include propylene, 1-butene, 1-pentemene, 4-methy, 11/-
1-pentene, 8-methy/L'-1-bentene, 1-
hexene, 1-octene, 1-decene, 1-dodecene,
1-Hexadecene is an example of ◇ In addition, the ethylene-α olefin rubber referred to in the present invention is exemplified, and the ethylene-α olefin non-conjugated diene rubber or a mixture thereof is exemplified. is 1
．． 4-hexadiene, 1,7-octadiene, 5-ethylidene-2-)μbornene, 5-vinyl-2-noiv*bone, 5-ethylene-2-no/L/lNμbonene, dicyclopentane Jen et al., and 2 selected from these
An example is a system in which more than one species is used in combination.

Particularly suitable compositions for the present invention include mixtures of ethylene-propylene-Q clopentadiene rubber and ethylene-propylene-ethylysinobornene rubber, or mixtures of ethylene-propylene-cyclopentadiene rubber and ethylene-1q-cyclopentadiene rubber.
- A mixture of putene-ethylidene and μ-bornene rubber is exemplified. The sponge compound composition according to the present invention contains the above-mentioned rubber as a main component, and also contains relatively small amounts of other synthetic rubbers, natural rubbers, or synthetic resins. Also, fillers such as carbon black, talc, clay, μsium carbonate, etc., processing agents, softeners, proscene oil, and anti-aging agents can be added.

Examples of vulcanizing agents include, but are not limited to, sulfur, organic peroxides, etc., and vulcanization aids and vulcanization accelerators are also appropriately selected and used depending on each vulcanizing agent. For example, orthobisulfonylhydrofusin (OBSH), Azocica μbonic acid amide (AZC), dinitrosopentamethylenetetramine (DPT), etc. may be used alone or in combination.◇These rubbers The necessary amounts of various materials are kneaded using a Banbury mixer, a kneader, and a Ro 1VI4 kneading machine, and the sponge compound composition and the postmortem are subjected to electron beam irradiation treatment. The acceleration voltage and the irradiation line i are determined as the irradiation conditions in which the irradiation device and the irradiation conditions are selected.
%irradiation! ! The amount is I Mrad or Q Q Mr
ad is used, and the increase or decrease is adjusted as necessary ◎ The molded product subjected to electron beam irradiation treatment is then vulcanized in a mature air vulcanizer, a UHF vulcanization method, a moving bed vulcanization tank, or a vulcanization can. After sulfurization and foaming, a sponge product with the desired improved surface texture is completed. As sponge products, in addition to those made of a single sponge, so-called sponge solid composites, which are a composite of sponge and non-foamed rubber, are also suitable objects of the present invention.

Examples are shown below, but the present invention is not limited thereto.Example 1. Comparative Example 1 Table 1 Comparative Example 1: Vulcanization accelerator (product of Sumitomo Chemical Co., Ltd.) The formulation shown in Table 1 was kneaded using a Banbury mixer and Mixing Glow to obtain a KPDM rubber composition for foam. - This rubber composition is extruded using a 45 φ extruder (dice 100°C).
After extrusion molding into a rectangular shape and irradiating the surface of the extrusion molded product with an electron beam, it was heated in a hot air tank at 280°C for 5 minutes.
A rubber foam was obtained by vulcanization foaming.

The evaluation of the surface skin of the obtained rubber foam and the specific gravity of the rubber foam are shown in Table 2. As usual, the conventional synchropentadiene EPD
By applying electron beam irradiation, it is possible to easily obtain a highly foamed low specific gravity sponge with good sponge skin, which was thought to be impossible with M.

Examples 2-4. Comparative Examples 2 to 6 Examples of the present invention in sponge compositions using a combination of synchropentadiene-based BPDM and ethylidene norbornene-based EPDM are shown.

Table 8 Rice 1 Synchropentadiene EPDM%ML, +41
00℃ 70. Bu-tetrapyrene al'j'k 85 vr
t%, iodine value 20 *-Ethylidene, rubornene EPDMML
,, 100°C 78, 6 vyi @ amount 40 wt*, iodine value 20 The compound shown in Table 8 was kneaded in the same manner as in Example 1, and the obtained rubber composition was put into a 45811 extruder. , extrusion molded using a Garvey die at a die temperature of 100°C,
After electron beam irradiation in the same manner as in Example 1, vulcanization and foaming were performed in a hot air bath.

The obtained results are shown in Table 4. According to Table 4, by combining dicyclopentadiene EPDM with electron beam irradiation, a sponge product with good extrudability and sponge surface texture can be obtained. It is obvious〇

Claims (1)

[Claims] In a method for producing a sponge product by vulcanizing and foaming a molded product of a sponge compound composition made of an ethylene-α-olefin rubber containing ethylene-α-olefin-dicyclopentadiene rubber as a main component, the molded product is exposed to an electron beam. A method for producing a sponge product with improved surface texture, characterized by performing vulcanization and foaming after irradiation treatment.