JPS58138742A - Crosslinking of ethylene-vinyl acetate copolymer - Google Patents

Abstract

PURPOSE:A composition containing EVA and a crosslinking agent is previously dehumidified to less than a specific level, then heated to effect crosslinking, thus enabling uniform crosslinking without any adverse effects on its gel fraction and gel swelling. CONSTITUTION:A composition consisting of an ethylene-vinyl acetate copolymer, a crosslinking agent, when necessary, a crosslinking assistant,and a filler is previously dehumidified so that the water content of the composition becomes less than 0.15wt%, preferably less than 0.05wt%, and then heated, without moisture adsorption, at a temperature over the decomposition point of the crosslinking agent to effect crosslinking. The composition is dehumidified by placing it in a vessel containing a drying agent such as silica gel or heated with hot air or infrared rays. As a crosslinking agent, is mainly used an organic peroxide and it is preferred that a variety of polyfunctional compounds are used as a crosslinking assistant in the combination with an organic peroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for crosslinking ethylene-vinyl acetate copolymers.

Conventionally, in order to improve the mechanical performance of ethylene-vinyl acetate copolymers (hereinafter referred to as GV), a method of crosslinking AM has been used. Mixture tm is one that is heated to a temperature higher than the decomposition temperature of the organic roadside material and is cross-linked.

However, in WA, the content of ethylene groups and acetate groups is not constant, and the degree of crosslinking differs markedly due to the difference, and even though it is crosslinked, the mechanical strength improves slightly. [
0 - In addition, electron beam YrIl! is used as a crosslinking method for iv membrane. It is proposed in Japanese Patent Publication No. 56-4563. However, since the use of electron beams requires enormous equipment and expense, chemical crosslinking using organic peroxide as described above is desired.

Real WI! EV developed using chemical cross-linking method in response to requests from 4 companies
We conducted intensive research on the cross-linking of 1cVA as a result.
+1 The present invention was achieved by discovering that a small amount of water contained in the liquid has an extremely important effect on the degree of crosslinking and the crosslinked structure. Crosslinking aid.

In the method of adding a filler and heating the material to crosslink it, the moisture contained in the composition is reduced to 0.15% by weight or less. Moisture: Crosslinking is carried out by heating to a temperature above the decomposition temperature of the crosslinking agent without absorbing moisture.The main method is to heat the four moieties to a point at which a crosslinking reaction with an organic peroxide-based crosslinking agent occurs. ◎Removal of this moisture cannot be explained in detail, but if moisture is present during crosslinking of EVA, the rle fraction and r It is thought that this significantly affects the degree of swelling of the crosslinked fibers and inhibits the uniformity of the crosslinked fibers (4!1). This effect is particularly pronounced when crosslinking is carried out using an organic peroxide crosslinking agent alone, but when a polyfunctional hexamer is used in combination with the crosslinking agent as a crosslinking accelerator. Therefore, in the method of the present invention, it is sufficient to carry out the process in the absence of water in gvA, but the crosslinking agent added to gvA,
Crosslinking aid.

If the filler contains moisture, this moisture will cause
Since the cross-linking of IVA-jX is inhibited, add a cross-linking agent and a cross-linking aid) and a filler to the regular 9-group to dehumidify the 9-ll & hydrate to remove the moisture in the 4-layer. .

In addition, in the method of the present invention, the water content in gvA is limited to 0.15% by weight or less; however, the lower the water content, the less V% mechanical crosslinking reaction will proceed), and it is preferably 0.1% by weight.
Hereinafter, it is preferable to further reduce the amount to 0.05 weight or less. The method for measuring this water content is to use a small piece of a mixture (weight W,
) is left for KIG days in a dencator containing silica dal in advance, and if the weight at that time is W, -W Water content in small pieces (911 straw-Ar-xxo.

In addition, the composition of ffA in the method of the present invention is not particularly limited, but it has a vinyl acetate content of 5 to 5.
If the vinyl acetate content is less than about 40, a crystalline polymer is used. The above is an amorphous or rubber-like 4!
, -, so it can be selected according to the intended use.Additionally, a small amount of f, such as polyethylene, polypropylene, chlorinated polyethylene, or tem, such as ethylene glopylene, butyl tm, etc., can be added to am. The crosslinking agent used in the method of the present invention is mainly an organic peroxide compound, such as dichloride oxide, t-butyl/darpenezoate, 1,1-di(t-butyl/ mother oxy) -3,3,6-trimethylcyclohexane, 2゜2-bis-(S-butyl-oxy) ditane.

2.5-r-(t-tutylno-oxy)-2,
5-dimethylhexane, 1,4-bis-(t-testerΔ
-oxy)zoisoglobilbenzene, 2,5-dimethyl-2,5-di(t-!thylperoxy)hequinane-3
etc.

Further, as a crosslinking aid, it is preferable to use various polyfunctional compounds in combination with an organic peroxide, such as nato-2methylolmethanetetraacrylate.

Trimethylolmethane triacrylate, tri) 1 f
To R-! ronodantriacrylate), Silf Lengelicol dimethacrylate, and Toshiaryencyanurate.

Also, if necessary, calcium sulfate A, aluminum hydroxide,
Inorganic fillers such as ayulite and clay, halodane flame retardants, lubricants, #1 surface treatment agents.

You may add one antioxidant, one blowing agent, one coloring agent, etc.

Further, dehumidification treatment in the method of the present invention includes, for example, a method of keeping the above-mentioned mixture closed with KlF in a container containing a desiccant agent such as silica dal, a method of heating and drying with hot air or far infrared rays, a method of blowing dry gas, etc. This can be done by attaching a powder, low temperature drying method, vacuum drying method, etc.

Next, examples of the present invention will be described. Example 1 and Comparative Example 1 EVA (Mitsui 4S4R) with a vinyl acetate content of 25% by weight
i Rikini Co., Ltd., EVA FLUX-360)
IVA with a vinyl acetate content of 40 parts by weight and 61 parts by weight (manufactured by Dainippon Ink & Chemicals Co., Ltd., "EVA'l'H" ■4
5G-P) to 100 parts by weight of the resin, 1.8 parts by weight of Cimiquil t4-Oxai I' and 1.8 parts by weight of Cimiquil t4-oxai I' and 100 parts by weight of the resin containing 60 parts by weight of Trimetalug μ/arm triacrylate (Shin Nakamura Chemical Co., Ltd.). Mu-TMPT manufactured by Co., Ltd.
) A mixture consisting of 0.7 parts by weight of calcium stearate and 1 part by weight of calcium stearate was mixed in a kneader and then pelletized.

This pellet was made into a sheet KMill9 with a thickness of 3 mm by using a T6Sφ extruder at a temperature at which the peroxide does not decompose.The resin temperature was 110°C.

This sheet was made into small pieces of 10()
The mixture was heated for a minute to cause crosslinking, thereby obtaining an electrically bridged am.

In addition, in order to compare with the method of the present invention, the above-mentioned small piece was left in a warehouse for 3 days, and after death, it was heated at 150 CK to perform crosslinking to obtain a comparative electric bridge EV.

Example 2, Comparative Example 2 ZV membrane with vinyl acetate content of 2s (trade name: Sim FI)
JX-360) 40 parts by weight and vinyl acetate amount 61
- (Product Name Shim THLWNI -450-1')・0
The resin component consisting of parts by weight was dehumidified in advance for 24 hours in a 0.5 Torr vacuum drying oven, and then added to it, while preventing moisture absorption from the air, was added dicumyl/Mana-Oxide L, 5 parts by weight, and trimethyl chloride. Lupro af triacrylate 0.7
parts by weight and 1 part by weight of calcium stearate,
This composition was extruded into sheets of three thicknesses using an extruder under the same conditions as in Example 1, and for comparison purposes, the resin content was not subjected to any dehumidification treatment. A 3-inch thick sheet was extruded in the same manner using the same method.

Then, each sheet was crosslinked in the same manner as in Example 1.

The ratio, degree of swelling, and appearance of the product of the present invention and the comparative product were measured, and the results are shown in Table 1.
◇ In Table 1, the rle fraction and degree of swelling were measured using a Soxhlet extrusion machine and extruded with xylene for 25 hours as sm.〇 As detailed above, the method of the present invention According to this method, a crosslinked shim* shape having a low degree of swelling in solvents and a good appearance can be obtained, and its practical effects are extremely great.

Claims (1)

[Claims] In the method of adding a crosslinking agent and, if necessary, a crosslinking aid and a filler to an ethylene-acetate C-L copolymer and heating the mixture, the water contained in the composition is removed to zero. ．．
1. A method for crosslinking an ethylene-vinyl acetate copolymer, which comprises heating the crosslinking agent to a temperature above the decomposition temperature of the crosslinking agent without absorbing moisture after the ethylene-vinyl acetate copolymer is moistened to 15% by weight or less.