JPH06126894A - Polyethylene/rubber composite adhesive - Google Patents

Abstract

PURPOSE:To provide a polyethylene/rubber composite adhesive in which normal polyethylene having excellent processability is rigidly adhered to a rubber material. CONSTITUTION:A polyethylene sheet having less than 1,000,000 of molecular weight irradiated with an electron beam and rubber composition containing raw material rubber having a critical surface tension gammac of 27-35 millinewton/ meter are adhered integrally.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an adhesive composite of polyethylene and rubber.

[0002]

2. Description of the Related Art Polyethylene has higher rigidity than rubber and high weather resistance. Therefore, if it can be made into a composite material with rubber, it can be used for conveyor belts, hoses,
It is possible to improve various performances such as improving the performance of rubber products such as rubber linings. However, ordinary polyethylene having a molecular weight of less than 1 million has poor adhesion to a rubber material, and if it is vulcanized and adhered to unvulcanized rubber, gas generated from the unvulcanized rubber causes bubbles. was there.

The inventor of the present invention has previously proposed that if one million or more ultra high molecular weight polyethylene is used, the sheet can be firmly bonded and integrated to the unvulcanized rubber material simultaneously with vulcanization. However, since ultra-high molecular weight polyethylene is obtained as a powder with poor processability, in order to mold it into a sheet,
A sheet could not be obtained unless the powder was formed into a cylindrical shape by, for example, sintering and then cut into a sheet. Therefore, the ultra-high molecular weight polyethylene sheet becomes very expensive, and it is inevitable in terms of cost to obtain a composite material with rubber.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyethylene / rubber adhesive composite in which ordinary polyethylene having a molecular weight of less than 1,000,000 and excellent in processability can be firmly adhered to a rubber material. .

[0005]

Means for Solving the Problems The present invention which achieves such an object is to provide a polyethylene sheet having a molecular weight of less than 1,000,000 irradiated with an electron beam and a critical surface tension γc of 27 to 35 millinewtons / meter (hereinafter referred to as mN / m). The rubber composition containing the raw material rubber (abbreviated) is integrally bonded.

As described above, according to the present invention, a polyethylene sheet having a molecular weight of less than 1,000,000 irradiated with an electron beam and a rubber composition containing a raw material rubber having a specific γc are adhered under heating to firmly bond the two. Integrate and coat the surface of the rubber product with polyethylene, or use different rubber materials with polyethylene as an adhesive medium, such as ethylene-propylene-diene copolymer rubber (EPDM) and styrene-butadiene copolymer rubber (SBR). Can be a rubber-rubber adhesive composite.

The polyethylene used in the present invention has a molecular weight of 100 produced by a conventional high pressure method, medium pressure method or low pressure method.
It is less than 10,000 polyethylene and can be easily formed into a film or other sheet-like shape by melt extrusion. This polyethylene sheet is irradiated with an electron beam before adhering to the rubber material. The electron beam preferably has an irradiation dose in the range of 3 to 10 Mrad in intensity. By setting the irradiation dose of the electron beam to 3 Mrad or more, the adhesion of the polyethylene sheet to the rubber material can be improved. Also, the irradiation dose of the electron beam is 10
By setting it to be Mrad or less, the mechanical strength and flexibility of the polyethylene sheet can be secured and the polyethylene sheet can be easily handled.

The polyethylene has a molecular weight of less than 1 million. In this way, since the molecular weight is not increased to the ultra high molecular weight range, the original excellent moldability of polyethylene can be maintained. The thickness of polyethylene sheet is 20-5
The range of 00 μm is preferable. When the thickness is 20 μm or more, it is possible to obtain a product having a uniform thickness, excellent handleability during the bonding work, and high adhesive strength. On the other hand, when the thickness is 500 μm or less, it is possible to prevent the adhesive layer from becoming too thick and impairing the physical properties of the rubber material.

The rubber material used in the present invention is selected from a rubber composition containing a raw material rubber having a critical surface tension γc of 27 to 35 mN / m. More specifically, when the rubber material used for the adhesion treatment is unvulcanized rubber, γc = 27 to 35 mN
/ M, and in the case of vulcanized rubber γc = 27 to 32 mN / m
Is selected. When γc is out of the above range, the polyethylene sheet cannot be firmly bonded even if it is previously irradiated with an electron beam.

Here, the critical surface tension γc means a solid as described on August 20, 1978 (3rd printing), Maruzen Co., Ltd. "Chemical Handbook", Basic Edition II, page 618. If the contact angle of a homologous series of liquid hydrocarbons and other organic liquid compounds on the surface is θ and the surface tension of the liquid is γ, then cos
The relationship between θ and γ is almost a straight line regardless of the type of homologue. At this time, it is defined to mean a value of γc corresponding to θ = 0, that is, cos θ = 1. However, the critical surface tension γc of the raw material rubber defined in the present invention refers to a value similarly measured using a rubber sample obtained by flattening the raw material rubber whose γc is to be measured by hot pressing, instead of the above solid. .

As the raw material rubber having γc in the range of 27 to 35 mN / m, isobutylene-isoprene copolymer rubber (IIR: γc = 27 mN / m), ethylene-
Propylene-diene terpolymer rubber (EPDM: γc
= 28 mN / m), natural rubber (NR: γc = 31 mN /
m), polybutadiene rubber (BR: γc = 32 mN /
m), styrene-butadiene copolymer rubber (SBR: γ
c = 33 mN / m). These raw rubbers include a predetermined amount of a vulcanizing agent such as sulfur, a reinforcing agent such as carbon black,
An antioxidant, a vulcanization accelerator, and other compounding chemicals are compounded, and the compounding amount of the raw rubber is preferably at least 50% by weight or more.

The obtained rubber composition is molded into a rubber material having an arbitrary stackable shape such as a sheet or plate. These rubber materials may be reinforced by metal cords such as steel cords and cords made of various organic fibers such as nylon, polyester and aramid. When the polyethylene sheet irradiated with the electron beam is bonded and integrated on at least one surface of the rubber material, an adhesive composite having a surface covered with the polyethylene sheet can be obtained. Also, when sandwiching both sides of an electron beam irradiated polyethylene sheet with a rubber material in a sandwich form to bond and integrate them, rubber materials containing different raw material rubbers that could not be directly bonded so far, for example, unvulcanized. EPDM and SB
R and R can be vulcanized and bonded using a polyethylene sheet as an adhesive medium.

In the method for producing the polyethylene / rubber adhesive composite of the present invention, when the electron beam irradiated polyethylene sheet and the unvulcanized rubber material are adhered to each other, a raw material having a γc of 27 to 35 mN / m is used as the rubber material. An unvulcanized rubber composition containing rubber may be used and may be adhered simultaneously with vulcanization under heating. When bonding vulcanized rubber material,
A vulcanized rubber composition containing a raw material rubber having a γ c of 27 to 32 mN / m may be used as a rubber material, and may be integrally bonded under heating. The heating temperature in these adhesion treatments is not lower than the melting temperature of the electron beam irradiated polyethylene sheet, preferably not lower than 130 ° C. However, if the heating temperature is set too high, the polyethylene sheet or the rubber material will be deteriorated.

[0014]

【Example】

Experimental Example 1 Five kinds of rubber composition No. 1 having the composition shown in Table 1
(Raw material rubber IIR), No. 2 (Raw material rubber EPDM), N
o.3 (Raw material rubber NR), No.4 (Raw material rubber IIR / SB
R) and No. 5 (raw rubber NBR) was prepared, and a sheet-shaped unvulcanized rubber material having a size of 150 mm × 50 mm × 2.5 mm was molded.

On the other hand, a medium-pressure polyethylene is melt-extruded to form a film having a thickness of 100 μm, and an electron beam of 8 M is applied.
Then, a polyethylene sheet was prepared by rad irradiation and electron beam irradiation. 20 kg / cm ^{2 of} each of these five types of unvulcanized rubber materials and the electron beam irradiation polyethylene sheet
The adhesiveness when heated and integrated at 160 ° C. for 20 minutes under pressure was evaluated by the following method. The results are shown in Table 2.

Adhesion evaluation method : width 20 from adhesive composite
A mm sample was prepared and a peeling test was performed. At this time, when interfacial peeling occurred, the adhesiveness was evaluated as poor (x) even if the adhesive strength was high. On the other hand, when the interfacial peeling did not occur, a sheet with a thickness of about 0.5 mm was cut out with a razor, centering on the adhesive interface of the adhesive composite, and scratched near the adhesive interface of this sheet with a razor. A peeling test was carried out, and when the sheets were firmly adhered so as to cause cohesive failure inside, the adhesiveness was evaluated as good (◯).

[0017]

Further, * 1: N-phenyl-N'-isopropyl-p-phenylenediamine * 2: Nt-butyl-2-benzothiazolesulfenamide * 3: tetramethylthiuram monosulfide * 4: benzothia Jill disulfide From Table 2, unvulcanized rubber composition No. containing a raw material rubber having γc of 27 to 35 mN / m. All of 1 to 4 had good adhesiveness (◯). On the other hand, γc is 35 mN /
unvulcanized rubber composition No. 1 containing a raw material rubber (NBR) in excess of m. No. 5 was poor in adhesiveness (x).

Experimental Example 2 In Experimental Example 1, an adhesive treatment was carried out in the same manner except that the prepared rubber material was vulcanized, and the adhesiveness of these five kinds of polyethylene / rubber adhesive composites was evaluated by the above-mentioned method. The results are shown in Table 3. From Table 3, all of the vulcanized rubber compositions No. 1, 2, and 3 containing the raw material rubber having γc of 27 to 33 mN / m had good adhesiveness (◯). On the other hand, γc is 32 mN / m
The vulcanized rubber compositions No. 4 and No. 5 containing the raw material rubbers SBR and NBR in excess of 10% each had poor adhesion (x).

Experimental Example 3 The unvulcanized rubber composition No. 2 (raw rubber EPDM) and the unvulcanized rubber composition No. 4 (raw rubber SBR / NR) shown in Table 1 were directly pressed to each other to give a pressure of 20 kg / cm. ^Under pressure of ² , 160
Vulcanization adhesion was performed at 20 ° C. for 20 minutes, but the adhesion was poor (x). On the other hand, both rubber composition Nos. Two
And No. 4 and 20, and the electron beam irradiation polyethylene sheet used in Experimental Example 1 was interposed and laminated, and 20 kg / cm
^When it was vulcanized at 160 ° C. for 20 minutes under pressure of ² and bonded, it was firmly bonded and integrated, and the adhesiveness was good (◯). On the other hand, those obtained by vulcanizing and adhering with a polyethylene sheet interposed without irradiating with an electron beam had poor adhesion (x) and many bubbles were generated.

[0021]

According to the present invention, a polyethylene sheet having a molecular weight of less than 1,000,000 irradiated with an electron beam and a rubber composition containing a raw material rubber having a specific γc are adhered to each other under heating, whereby both are firmly bonded. Since they can be bonded and integrated, the surface of the rubber product can be coated with polyethylene, or a rubber-rubber adhesive composite made of different rubber materials using polyethylene as an adhesive medium can be formed.

Claims (1)

[Claims] 1. A polyethylene / rubber adhesive composite in which a polyethylene sheet irradiated with an electron beam and having a molecular weight of less than 1,000,000 and a rubber composition containing a raw rubber having a critical surface tension γc of 27 to 35 millinewtons / meter are integrally bonded. body.