JPS61152759A - Thermoplastic rubber composition used in drinking water tanks and their peripheral accessories - Google Patents

Abstract

PURPOSE:A composition that is composed of a styrene block copolymer, a low-molecular-weight olefin, an olefinic processing aid and a plasticizer oil, thus being suitable for use as water tanks and their peripheral equipment, because it resists deterioration caused by chlorine in drinking water, causes no migration of the plasticizer into water and has reduced permanent compression set. CONSTITUTION:The objective composition is obtained by using (A) 30-60wt% of a styrene block copolymer (SEBS), (B) 15-30wt% of a low molecular weight olefinic softenic agent (PIB) (C) 5-30wt% of a plasticizer oil and (D) 5-30wt% of an olefinic processing aid. Component A is preferably a styrene-ethylene- butylene-styrene block copolymer of 10-50wt% of styrene and 10,000-300,000 mol.wt. component B has preferably molecular weight of 30,000-50,000. Component D is preferably polypropylene or an ethylene-propylene block copolymer.

Description

[Detailed description of the invention] [Field of industrial application] The present invention is characterized by low deterioration due to chlorine etc. in drinking water, low migration of plasticizers etc. to water, and low compression set. This invention relates to thermoplastic rubber used in drinking water tanks and their peripheral equipment.

[Conventional technology]

Thermoplastic compounds are more useful than vulcanized rubbers and the like in that the mastication process and compounding agent kneading process can be simplified and the vulcanization process is unnecessary. In addition, since scrap can be reused, there is a great advantage in terms of resource conservation.

Conventionally, such thermoplastic rubbers include styrene thermoplastic rubber (TPS) and olefin thermoplastic rubber (TPS).
PO), PVC thermoplastic rubber, polyurethane thermoplastic rubber, polyester thermoplastic rubber, polyamide plastic rubber, etc. are known, but many of these have higher hardness than vulcanized rubber, which is a similar product group. However, it has the drawback of high compression set, and its range of use is quite limited.

[Problem to be solved]

Among these plastic rubbers, styrene-based plastic rubber has a relatively small compression set, but in this case, a large amount of plasticizer is blended, resulting in extremely low hardness, and depending on the use, styrene-based plastic rubber has a relatively low compression set. Conventional styrene-butadiene-styrene plastic rubbers also have 2
Due to the presence of heavy bonds, drinking water deteriorates significantly due to chlorine, making it difficult to use for water diversion.

[Means to solve problems]

The present invention aims to provide a rubber compound that solves the above-mentioned problems.
) A low molecular weight olefin softener, C) a plasticizer, and D) an olefin processing aid, and if necessary, an olefin rubber modifier and filler are added thereto.

Since the composition of the present invention has a low migration of plasticizer from the rubber, it can be usefully used as gaskets and sealants for food and medical containers, instruments, tubes, and construction.

Furthermore, since the composition of the present invention has a small compression set, when used as a puff agent, it maintains watertightness and airtightness for a long period of time.

Furthermore, since it is less susceptible to deterioration due to chlorine, it is particularly effective as a sealing material for drinking water tanks, packing materials for drinking water pumps, etc., and hoses.

The present invention will be explained in detail below.

A) styrenic block copolymer used in the present invention, hastyrene-butadiene-styrene-block copolymer,
Styrene-isoprene-styrene block l [c combination,
A styrene-ethylene-butylene-styrene block copolymer, etc., and preferably has a molecular weight of 10,000 to 3.
It is 00000. Also, the styrene content is 10-50
% by weight, preferably 10-35% by weight. Also, as a blend, the present copolymer is used in an amount of 30 to 60% by weight. Among the above-mentioned styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers are particularly useful because they are excellent in chlorine resistance, weather resistance, heat resistance, ozone resistance, and oil resistance.

B) The low molecular weight olefin softener used in the present invention is a low molecular weight olefin polymer such as liquid polychloroprene, liquid isobutylene-isoprene copolymer, liquid polyisoprene, liquid polybutadiene, low molecular weight polyisobutylene, and low molecular weight atactic polypropylene. There is a molecular weight of 10,000 to 50,000 MV (annual average molecular weight)
30,000 to 50,000 is particularly preferred, and the blending amount is 15 to 35% by weight, preferably 25 to 30% by weight.

C) Plasticizers used in the present invention include castor oil, tall oil, paraffin oil, naphthenic oil, and the like. Among these, paraffin oil and naphthenic oil with a viscosity (room temperature) of 90C5T or higher are good, especially 300C
Oils of 3T or higher provide better formulations with less migration from the rubber.

D) The olefin processing aid used in the present invention is polyethylene, polypropylene, ethylene-propylene copolymer, etc. Among them, polypropylene and ethylene-propylene block copolymer are preferred, and the blending amount is 5 to 50%.
30% by weight, preferably 10-15% by weight.

In the present invention, it is also effective to add E) an olefin rubber modifier to change (mainly reduce) the hardness of the compound and to reduce costs. E) As the olefin rubber modifier, an ethylene-propylene rubber copolymer, particularly an ethylene-propylene-diene terpolymer is preferable, and the blending amount is equal to the total polymer (AND).
20 to 150 parts by weight per 100 parts, preferably 30 parts by weight
~70 parts by weight. Also, good properties can be obtained even when E) is crosslinked by means such as dynamic vulcanization.

If the amount of this olefin rubber modifier is too small, the hardness will be high, and if it is too large, the compression set will increase at high temperatures (60° C. or higher), which is not preferable.

In the present invention, in addition to the above-mentioned components, F)
Fillers, reinforcing agents, etc. are appropriately blended.

These fillers and reinforcing agents include clay, talc, lucium carbonate, magnesium carbonate, white carbon such as silica and lucium silicate, barium sulfate, mica,
Palite powder, asbestos, graphite, ferrite,
There are carbon black, organic fibers, inorganic fibers such as carbon fibers, glass fibers, metal fibers such as aluminum, copper, brass, etc., and metal flakes, etc., which are selected and blended depending on the purpose.
By blending carbon black, ferrite, surface-treated mica, surface-treated glass fiber, carbon fiber, metal fiber, metal flake, etc., conductivity and electromagnetic shielding properties can be imparted.

In addition, other general-purpose compounding agents such as colorants, stabilizers, tackifying resins, etc. can be added within the range that does not impair the purpose of the present invention.

The present invention has the above-mentioned structure, and according to the present invention, a compound having a well-balanced hardness, compression set, and plasticizer migration can be obtained.0 The compound of the present invention has a hardness of 50 to 75 (JISA
) and compression set (JISK6301, go” C
Thermoplastic rubber formulations with x22HR5) in the range from 30 to 55% are obtained.

Moreover, since the thermoplastic rubber compound of the present invention has extremely low migration of plasticizer from the rubber, it is used in a compressed state between flanges and with bolts and nuts, etc. Application 1: For example, as a sealing material for a prefabricated water tank for drinking water; It is particularly suitable for use in drinking water piping flange packings, hoses, etc. Furthermore, in addition to being used in peripheral machines for drinking water, it can also be usefully used in gaskets for housings of electronic devices such as computers, computer keyboards, sealing materials, backings, cushioning materials, tubes, hoses, mats, etc.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

The following experiments were conducted on formulations as shown in Table 1.

l) A sheet with a compression set thickness of 31 layers was compressed to 1 inch and heated at 80°C x 22H.
After being left as it was and being opened, the permanent set was measured.

2) Migration A sheet with a thickness of 41mm was compressed to 1mm, left at room temperature for 10 days, then opened, and the presence or absence of migration was measured.

3) Chlorine resistance A sheet with a thickness of 1 cm was immersed in 5% NaCl for 1 month.
The residual tensile strength was measured after several months.

These evaluation results are shown in the lower part of Table 1.

As can be seen from this table, the evaluation of the sheet based on the present invention was extremely high, and it was proved that it had superior properties in all evaluation items compared to the conventional examples.

Claims (1)

[Claims] (1) A) Styrenic block copolymer (SEBS) 3
0 to 60% by weight, B) low molecular weight olefin softener (P
IB) 15 to 30% by weight, C) plasticizer oil 0 to 30% by weight, and D) olefinic processing aid (PP) 5 to 30% by weight, and is a plasticizer with little deterioration due to chlorine etc. in drinking water. A thermoplastic rubber compound used for drinking water tanks and peripheral equipment thereof, which is characterized by low transfer to water and low compression set.