JPS6042819B2 - Polymer crosslinking method - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for crosslinking α-olefin and/or diolefin polymers (hereinafter referred to as polymers) excluding ethylene, and more specifically relates to a method for crosslinking α-olefin and/or diolefin polymers (hereinafter referred to as polymers) excluding ethylene. The present invention relates to a method for crosslinking a polymer, which comprises irradiating the polymer in an uncrosslinked molten state with ultraviolet rays.

Conventionally, it has been known to add an appropriate organic peroxide to a polymer to crosslink it for the purpose of improving the mechanical, chemical, and thermal properties of the polymer, and numerous studies have been conducted. . However, in these conventional methods, thermal crosslinking is carried out at a temperature higher than the decomposition temperature of the added organic peroxide, so the molded product to be crosslinked is susceptible to thermal deformation during crosslinking, and in order to prevent thermal deformation, a lower temperature is required. If the organic peroxide is decomposed on the side, the decomposition time becomes long, and the time required for the crosslinking reaction also has the disadvantage of exceeding several hours. The present invention aims to provide a method for crosslinking polymers that solves these drawbacks, and these methods involve irradiating ultraviolet rays to a polymer that contains an organic peroxide and is in an uncrosslinked molten state. achieved by

The inventors first incorporated an organic peroxide into polyethylene resin, and then irradiated polyethylene resin with ultraviolet rays at a temperature and time that were above the melting point of the resin and did not substantially crosslink with heat alone. A method for crosslinking resins was provided (Japanese Patent Application No. 52,586/1986), but as a result of further studies on other polymers, it became possible to easily use α-olefin and/or diolefin polymers other than polyethylene resin. The present invention was achieved by discovering that cross-linking occurs and further investigating this fact.

That is, the present invention involves incorporating an organic peroxide into an α-olefin and/or diolefin polymer excluding ethylene, heating and melting this mixture to a substantially uncrosslinked state, and under the conditions. This method is characterized by irradiating the polymer with ultraviolet rays to efficiently and uniformly crosslink the polymer. In this invention, the olefinic and/or diolefinic polymers other than ethylene include α-olefinic polymers such as propylene, butene-1, bentene-1, 4-methyl-bentene-1, hexene-1,
Diolefin-based homopolymers such as isoprene, 1●4-butadiene, 1●2-butadiene, etc., and α-olefin-based copolymers and dienes such as ethylene-propylene copolymers with an ethylene content of less than 50%. It also includes a synthetic rubber component, and also includes a mixture thereof or a mixture of the above-mentioned polymer as a main component with other polymers such as polyethylene resin. The organic peroxide referred to in this invention means a compound having a 10-0 bond in its molecule, and is effective in the crosslinking reaction of olefin and diolefin polymers, and is It has a decomposition temperature higher than that temperature and varies depending on the type of polymer.

For example, polymers such as ethylene propylene rubber have
1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1●3-bis(t-butylperoxyisopropyl)benzene, dicumyl peroxide, etc. are used. For the combination, 2●5-dimethylhexane 2●5-dihydroperoxide, 2●5-dimethyl 2●5-di(t-butylperoxy)hexane-3, cumene hydroperoxide, etc. are used. These organic peroxides are used in a proportion of 5 parts or less, preferably 0.1 to 2 parts, based on the polymer (10CE). Methods for incorporating organic peroxide into the polymer include kneading,
A method such as dissolving an organic peroxide in a suitable solvent and contacting and impregnating the solution with the solution is used. The crosslinked polymer obtained by this invention includes grains, plates, wires, films,
It does not matter whether it is a molded product, etc. The ultraviolet rays used in this invention have a wavelength of 1000A to 4000A, and particularly preferably 1850A to 4000A.

As these ultraviolet ray sources, low pressure, high pressure, ultra-high pressure mercury lamps, xenon lamps, carbon arcs, etc. are used. The heating in this invention is carried out at a temperature equal to or higher than the melting temperature of the polymer and under conditions where heating alone does not substantially result in crosslinking, which varies depending on the polymer and organic peroxide used. The atmospheric phase during ultraviolet irradiation may be either a gas phase or a liquid phase, and specific heating methods include heating with a heater, using radiant heat emitted from a silicone oil bath, an infrared lamp, and a high-pressure mercury lamp. However, this can be used as appropriate.

In the case of crosslinking by irradiating ultraviolet rays in this invention, a method of irradiating ultraviolet rays while continuously introducing a crosslinked molded article into a heating zone, a method of irradiating ultraviolet rays while heating in batches, etc. are used. However, this is not particularly limited.

By irradiating the organic peroxide-containing polymer with ultraviolet rays under conditions in which it is heated and melted in this way, a uniform crosslinked product can be obtained.

That is, crosslinking in the crystallized state below the melting temperature of the polymer is localized in the amorphous region of the organic peroxide resin, so the dispersibility of the organic peroxide within the polymer is poor. The crosslinking reaction occurs selectively in the amorphous regions of the polymer, resulting in a heterogeneous crosslinked product in which the crystalline regions remain uncrosslinked, whereas crosslinking at temperatures above the melting temperature of the polymer causes the crystalline regions to Since the organic peroxide is not present, the dispersibility of the organic peroxide is good, so that the crosslinking reaction occurs uniformly in the polymer, resulting in a uniform crosslinked product. In the case of amorphous polymers such as diolefin polymers or ethylene propylene rubber, which have almost no crystalline regions among polymers, there is no particular need to heat-melt them, but as in this invention, The crosslinking reaction of the polymer can be significantly accelerated by irradiating the polymer with ultraviolet rays while heating the polymer to a state where it is not substantially crosslinked by heat alone. This is because the decomposition of the organic peroxide occurs due to the synergistic effect of using thermal energy and ultraviolet energy at the same time. In other words, the -0-0 bond of the undecomposed organic peroxide, which has been activated to an excited state by absorbing thermal energy, is easily and selectively dissociated by the action of ultraviolet energy, resulting in crosslinking of the polymer. This seems to be because a large number of effective radicals are generated. On the other hand, when a polymer containing an organic peroxide is irradiated with ionizing radiation (e.g. accelerated electron beam) instead of ultraviolet rays, no accelerating effect on the crosslinking reaction of the organic peroxide is observed. Therefore, the crosslinking promoting effect in this invention is unique to ultraviolet energy.

The degree of crosslinking in this invention is defined by the weight percent of the insoluble polymer after placing the polymer in a 200-mesh wire mesh basket, performing reflux extraction using Soxhlet, and drying after extraction for a certain period of time. Depends on the combination.

The term "substantially uncrosslinked polymer" as used in the present invention means one in which the degree of crosslinking is zero. Furthermore, the melting temperature of a polymer refers to the temperature when the crystalline region of the polymer is in a molten state, and specifically, the melting curve is measured using a differential scanning calorimeter at a heating rate of 8°C/min. This refers to the peak temperature when

The present invention will be described below with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

Example 1 Ethylene propylene rubber (Mitsui EPT4O2l) 1 (
1 part and 1 part of 1,3-bis(t-butylperoxyisopropyl)benzene were dissolved in toluene, mixed and stirred, dried under reduced pressure, and then molded in a compression molding machine heated to 80°C to a thickness of 1.5 cm. An uncrosslinked ethylene propylene rubber sheet was made.

Next, the sheet was placed on a heating plate maintained at 1000C, and after preheating for 3 minutes to melt the sheet, a high-pressure mercury lamp (H-
400P type) was used for 5 minutes of ultraviolet irradiation. When the degree of crosslinking of the obtained crosslinked sheet was measured, it was found to be 60.
%Met. The degree of crosslinking is the dry weight % of n-hexane insoluble matter after reflux extraction with n-hexane for 6 hours.
For comparison, the uncrosslinked ethylene propylene rubber sheet prepared above was used for 10 days without UV irradiation.
Crosslinking treatment using only heat was performed for 5 minutes at 0°C, and the degree of crosslinking was measured. It was 0%.

As is clear from the above results, when crosslinking treatment is performed only by heat, no degree of crosslinking is obtained, whereas
When crosslinking treatment is performed by irradiating ultraviolet rays under heating conditions of 100'C, high crosslinking occurs in a short time. - degree was obtained, indicating that the crosslinking efficiency was excellent.

Example 2 1 part of dicumyl peroxide was mixed with 100 parts of Syndiotactic 1/2 polybutadiene resin (JSR..RB82O manufactured by Japan Synthetic Rubber Co., Ltd.), and the mixture was heated at 120°C in a 20 mm diameter extruder. Melt and knead to make pellets, and then add 1
A compression molding machine heated to 20℃ has a thickness of 1.5? An uncrosslinked Syndiotactic 1,2 polybutadiene sheet was prepared.

Next, UV rays were irradiated for 5 minutes under the same conditions as in Example 1, and the degree of crosslinking was measured under the same conditions as in Example 1, and it was found to be 78%.
It was hot. For comparison, the uncrosslinked Syndiotactic 1/2 polybutadiene sheet prepared above was crosslinked by heat alone at 100°C for 5 minutes without UV irradiation, and the degree of crosslinking was measured. However, it was 0%. As described above, the present invention is also effective when using Syndiotactic J1.2 polybutadiene resin.

Example 3 Powder 1 of ethylene-propylene block copolymer (ethylene content 8% by weight, MIL.Ol melting temperature 162°C)
1) part and 2 parts of 2,5-dimethyl 2,5-di(t-butylperoxy)hexene-3 were dissolved in toluene, mixed and stirred, dried under reduced pressure, and then molded to a thickness using a compression molding machine heated to 170°C. 1.5 wL of uncrosslinked sheet, then 170°C
The above-mentioned sheet was placed on a heating plate held at a heating plate, and after melting, ultraviolet rays were irradiated from above the sheet for 7 minutes in the same manner as in Example 1.

When the degree of crosslinking of the obtained crosslinked sheet was measured, it was found to be 4.
It was 5%. The degree of crosslinking is the dry weight % of insoluble matter after immersion in tetralin at 135° C. for 3 hours. Also, for comparison,
Using the uncrosslinked sheet prepared above, crosslinking treatment was carried out by heat only at 170'C for 7 minutes without UV irradiation, and the degree of crosslinking was measured and found to be 0%.

Example 4 Ethylene propylene rubber used in Example 1 (Mitsui EP
T4O2l) (4) parts and 1 (1) part of the syndiotactic 1,2 polybutadiene resin (RB-820 manufactured by Nippon Gosei Rubber Co., Ltd.) used in Example 2 were added with 1,3-bis(t-butyl peroxide). Mix 1.5 parts of benzene (oxyisopropyl) to 20T! Melt and knead at 120°C using an Rmφ extruder to form granules, and then use a compression molding machine heated to 120°C to give a thickness of 1.5 Wr! An uncrosslinked sheet of RL was made.

Next, ultraviolet rays were irradiated for 5 minutes under the same conditions as in Example 1, and the degree of crosslinking was measured under the same conditions as in Example 1, which was 75%. For comparison, the uncrosslinked sheet produced above was subjected to crosslinking treatment using only heat at 100°C for 15 minutes without UV irradiation, and the degree of crosslinking was measured, and it was found to be 0%. Ta. As is clear from the above examples, according to the present invention, the crosslinking reaction of the polymer is significantly accelerated and a uniform crosslinked product can be obtained. It is applied to cross-linked foam sheets, cross-linked beads, etc., and its industrial value is extremely large.

Claims (1)

[Claims] 1. After incorporating an organic peroxide into an α-olefin and/or diolefin polymer excluding ethylene,
A method for crosslinking a polymer, which comprises heating and melting this mixture to a substantially uncrosslinked state and irradiating it with ultraviolet rays under the same conditions.