JPS5981321A - Production of modified polyolefin polymer particle - Google Patents

Abstract

PURPOSE:To obtain polyolefin polymer particles capable of providing foams of excellent quality, by heating a dispersion of crosslinked polyolefin polymer particles and a polymerizable monomer in which the polymer particles can dissolve or swell in an aqueous medium. CONSTITUTION:Precrosslinked polyolefin polymer particles and a polymerizable vinyl monomer in which these polymer particles can dissolve or swell are dispersed in an aqueous medium and heated to a temperature at least 5 deg.C above the softening point of the polyolefin polymer to effect both impregnation and polymerization of the polymerizable vinyl monomer simultaneously. When the above precrosslinked polyolefin polymer particles have a low degree of crosslinking, the polyolefin polymer particles impregnated with the polymerizable vinyl monomer unite partly, while when the degree of crosslinking is excessively high, the impregnation with the polymerizable vinyl monomer is retarded, and nonuniform impregnation or homopolymerization of the monomer are apt to occur. Therefore, the degree of crosslinking is preferably in the range of 10- 60wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a modified polyolefin polymer, and more specifically, the present invention relates to a method for producing a modified polyolefin polymer, and more specifically, a method for rapidly dissolving or swelling a polyolefin polymer with a polymerizable vinyl monomer that dissolves or swells the polymer. A method for producing polymerized polyolefin polymer particles impregnated with a polymerizable vinyl monomer, which uniformly impregnates the particles, performs impregnation polymerization of the polymerizable vinyl monomer in the polyolefin polymer position without particle coalescence, and provides a foamed molded product of excellent quality. It is related to.

Foam molded products obtained from polyolefin polymers, particularly polyethylene polymers, are excellent packaging materials that are strong, hard to break, and can withstand repeated use. Poor dimensional accuracy,
It has drawbacks such as the molded body being soft and having poor cushioning performance. This drawback is due to the low rigidity that is a characteristic of polyolefin polymers. As an improvement method, a method has been proposed in which a polyolefin polymer is impregnated with a polymerizable vinyl monomer, particularly a styrene monomer, and then polymerized.

The method of impregnating and polymerizing a polyolefin polymer with styrene monomer, etc. involves dispersing the polyolefin polymer positions in an aqueous dispersion medium, and dissolving a catalyst for polymerizing the styrene monomer etc. and a crosslinking agent for crosslinking the polyolefin polymer positions. Generally, a styrene monomer or the like is added, the styrene monomer or the like is impregnated into the polyolefin polymer, and then polymerized and crosslinked. When a polyolefin polymer is impregnated with styrene monomer or the like using this method, the impregnated polyolefin polymer positions are very likely to coalesce, and the coalesced particles solidify and form agglomerates as the impregnated monomer polymerizes. . If it is carried out at a high temperature such that the polyolefin polymer position melts, the polyolefin polymer itself will melt and be in a state where it is easy to fuse, so that it will be easier to coalesce. Therefore, it is usual to carry out the treatment at a temperature below the softening temperature of the polyolefin polymer. At this time, in order to uniformly impregnate the styrene monomer, etc., it is necessary to gradually add the styrene monomer, etc., and to take a long time for impregnation.

However, even in this case, since impregnation is difficult, there are drawbacks such as styrene monomer etc. polymerizing independently in water before impregnation.

As a method to facilitate impregnation, it has been proposed to use a specific polyolefin polymer with a low softening point or to add plasticizers such as dioctyl or luphthalate to the polyolefin polymer. The foamed molded product obtained from the produced styrene monomer-impregnated polyolefin polymer particles has reduced heat resistance and molded product dimensional stability, and the stiffness effect due to styrene monomer-impregnated polymerization is reduced.

Furthermore, the method of impregnating a polyolefin polymer with a styrene monomer or the like to polymerize and crosslink it has the disadvantage that a very large amount of crosslinking agent is required, probably because it is wasted in the polymerization reaction.

Furthermore, a method has been proposed in which a crosslinked olefin polymer is dissolved in a large amount of an organic solvent and then a methacrylate monomer is added thereto for polymerization. This method allows methacrylate to be impregnated at a temperature below the softening temperature of cross-linked polyolefin, but since it is dissolved in a large amount of solvent, it is very easy to fuse and coalesce, and it cannot be heated to high temperatures, requiring a long impregnation time. . Another drawback is that it requires a great deal of effort to remove the organic solvent used for dissolution after the polymerization is completed.

As a result of intensive research into a method for improving these drawbacks, the present inventors have found that by using a pre-crosslinked polyolefin polymer position, the crosslinked polyolefin polymer can be heated to a temperature higher than the temperature at which the crosslinked polyolefin polymer melts. The particles impregnated with Zuma are quickly impregnated without coalescing, the impregnation process is omitted, and even if impregnation and polymerization are performed at the same time, uniform impregnation is achieved.
In addition, no homopolymer of polymerizable vinyl monomer is generated, and polymerization can be performed using a smaller amount of catalyst than in polymerization and crosslinking after impregnation.

It was discovered that it can be crosslinked, leading to the present invention.

That is, in the present invention, a pre-crosslinked polyolefin polymer position and a polymerizable vinyl monomer that dissolves or swells the polymer position are dispersed in an aqueous medium, and heated to a melting temperature of the crosslinked polyolefin's softening point +5°C or higher, The present invention provides a method for producing a modified polyolefin polymer, which is characterized in that impregnation with a polymerizable vinyl monomer and polymerization are carried out in the same city.

The pre-crosslinked polyolefin polymers used in the present invention include ethylene, propylene, butene-1, pentene-1,
1,3-methylbutene-1,4-methylbutene-1,4
- Homopolymers or copolymers of monoolefins such as methylhexene-1,5-methylhexene-1, ethylene-vinyl acetate copolymers, ethylene-vinyl chloride copolymers, ethylene-methylmethacrylate-1. A copolymer of a monoolefin and another polymerizable vinyl monomer, such as a copolymer, or a mixture thereof is prepared by adding dicumyl per,
Organic peroxides, α-rays, β
- It is cross-linked by radiation irradiation such as radiation, and any MI
A polyolefin polymer having a certain value and softening point can be crosslinked and used.

The degree of crosslinking of the pre-crosslinked polyolefin polymer used in the present invention is determined by measuring the degree of crosslinking by measuring the insoluble content after extraction with boiling xylene for 24 hours. However, if the degree of crosslinking is low, some coalescence of the polyolefin polymer particles impregnated with the polymerizable vinyl monomer will occur, whereas if the degree of crosslinking is too high, impregnation of the polymerizable vinyl monomer will occur. This slows down the process and tends to cause non-uniform impregnation and the formation of homopolymers of polymerizable vinyl monomers. Therefore, the preferable degree of crosslinking in order to further exhibit the effects of the present invention is 10 to
A range of 60% by weight is preferred.

Polymerizable vinyl monomers that can be used in the present invention to dissolve or swell polyolefin polymers include styrenic monomers such as substituted styrenes such as styrene, α-methylstyrene, and p-methylstyrene; acrylonitrile, methyl methacrylate, and chloride. Examples include vinyl, vinyl acetate, etc. Among these, styrene monomers are particularly preferably used. The amount of such polymerizable vinyl monomer impregnated is not limited in the present invention, but a foamed molded product from a crosslinked polyolefin polymer position in which a large amount of polymerizable vinyl monomer is impregnated does not exhibit the characteristics as a polyolefin foam. If it is too small, the modification effect by impregnation polymerization of the polymerizable vinyl monomer will not be achieved. Therefore, the amount of the polymerizable vinyl monomer to be impregnated is preferably in the range of 5 to 200 parts per 100 parts of the crosslinked polyolefin polymer, depending on the quality of the product foam.

The polymerizable vinyl monomer is dispersed in a system in which a crosslinked polyolefin polymer is dispersed in water using a water-soluble polymer substance such as polyvinyl alcohol or methyl cellulose, or a poorly water-soluble inorganic substance such as calcium phosphate or magnesium pyrophosphate as a dispersant. The catalyst may be charged, impregnated, and polymerized, or the polymerization catalyst may be gradually added in a dissolved state to the system heated above the impregnation polymerization temperature.

The polymerizable vinyl monomer is impregnated into the crosslinked polyolefin polymer.The polymerization temperature must be such that at least a portion of the crosslinked polyolefin polymer is molten in order to impregnate the polymer quickly and uniformly. . The melting temperature of polyolefin polymers cannot be clearly measured, and the melting point is generally determined by the peak temperature of the heat of dissolution measured by a differential scanning calorimeter (DSC), but the melting point calculated using this method is below the melting point and above the softening point. Partial melting has occurred. ASTM-D-747
The temperature must be +5°C or higher than the softening point according to the measurement method of -70, preferably 72 or higher (softening boiling melting point), and the upper limit is the decomposition temperature and economic efficiency of the catalyst used for polymerization of the impregnated polymerizable vinyl monomer. The temperature is preferably about 160°C or less.

The catalyst used for the polymerization of the impregnated polymerizable vinyl monomer can be used as long as it is soluble in the monomer, but it must work effectively at the above impregnation and polymerization temperatures.
For example, those having a decomposition temperature of 60° C. or higher are suitable, such as di-t-butyl peroxide, dicumyl peroxide, [-butyl peroxylaurate, benzoyl peroxide, and t-butyl peroxyisobutyrate.

The polymerizable vinyl monomer-impregnated polymerized cross-linked polyethylene particles obtained by the present invention can contain propane, butane, pentane,
Aliphatic hydrocarbons such as hexano.

Cycloaliphatic hydrocarbons such as cyclobutane and cyclopenkune, methyl chloride, and ethyl chloride.

Trichlorochloromethane, dichlorochloromethane.

It is impregnated with a blowing agent such as a halogenated hydrocarbon such as dichlorodichloromethane, heated with steam to form foamed granules, and used for foam molding. Compared to conventional foam molded products obtained from crosslinked polyethylene particles, the foamed molded products made from the polymer particles of the present invention obtained by this method have a uniform and finer foam cell diameter, can be expanded to a high expansion ratio, and are more easily foamed. There is less contraction of time,
It has excellent properties such as increased rigidity of the molded product and improved cutability such as press cutting.

The present invention will be explained in more detail in the following examples.

Example 1 1.51 800cc of water and calcium phosphate 3. OF, sodium dodecylbenzenesulfonate 2
Styrene monomer 2007 in which 0.42 benzoyl peroxide was dissolved was added to the system in which 200 g of polyethylene particles with different degrees of crosslinking with a softening point of 91°C and a melting point of 107°C were added and dispersed at 00 mF, and heated to 105°C. The temperature was raised to , and the reaction was carried out for 5 hours.

After the reaction is complete, cool to 60°C or below, 7, take out, 7@j
: The table below shows the situation and particulate matter of the collaboration.

il:,:Pst...The effect of the difference in the presence or absence of styrene homopolymer crosslinking is obvious, with a degree of crosslinking of 10 to 60%, almost no scale particle adhesion, no styrene homopolymer powder, and rapid impregnation. Recognize.

Example 2 12Kp of 400% crosslinked polyethylene particles with a softening point of 95°C and a melting point of 112°C were added to an 801 polymerization machine, and 7 to 80% of styrene monomers were added to the 801 polymerization machine.
．． Calcium phosphate 200! i2. Sodium dodecylbenzenesulfonate 107. Add 35g of benzoyl peroxide and 40J of water, stir, and heat to 90°C and 100°.
Impregnation polymerization was performed at C, 110°C, and 140°C for 5 hours, respectively. The results are shown in the table below.

2007 water with 32 polyvinyl alcohol dissolved f
The mixture was dispersed in 300 cc, dicumyl peroxide i, ofI was added as a crosslinking agent, the temperature was raised to 150°C, the reaction was continued for 3 hours, and the mixture was cooled to 40°C to obtain polyethylene particles with a degree of crosslinking of 35%. 100 g of styrene in which 0.42 t-butyl peroxybenzoate was dissolved was added to this system,
After raising the temperature to 120°C and reacting for 4 hours, it was cooled to 60°C or lower and taken out.

There was no scale or coalescence of particles in the can, and there was no styrene homopolymer powder. Further, the obtained impregnated particles were impregnated with dichlorodichloromethane in the same manner as in Example 3, and foamed to obtain expanded particles having uniform and fine cells.

Same polyethylene particles 200! i', llnot -7"
Chil peroxybenzoate and 1.0 g of dicumyl peroxide were dissolved in 600 cc of water and dispersed.
Styrene impregnation for 3 hours at 120 °C, 4
After polymerization for an hour and further reacting at 150°C for 3 hours,
It was cooled and taken out. In this case, the discharged wastewater was emulsified with styrene homopolymer. Only 11% of the obtained crosslinked polyethylene was crosslinked, and the crosslinking efficiency of dicumyl peroxide was clearly lowered. The foamed particles obtained by impregnating the impregnated particles with dichlorodichloromethane and foaming were non-uniform cells with large cavities inside.

Patent applicant Kanebuchi Chemical Industry Co., Ltd. Agent: Patent attorney Makoto Asano

Claims (4)

[Claims] (1) Pre-crosslinked polyolefin polymer positions and a polymerizable vinyl monomer that dissolves or swells the polymer particles are dispersed in an aqueous medium, and the melting temperature is higher than the softening point of the polyolefin polymer by 4-5°C. A method for producing a modified polyolefin polymer, which method comprises heating, impregnating a polymerizable vinyl monomer, and polymerizing the polymer at the same time. (2) The manufacturing method according to claim 1, wherein the polymerizable vinyl monomer is a styrene monomer. (3) The production method according to claim 1 or 2, wherein the polyolefin polymer position is polyethylene and/or a copolymer arm of polyethylene. (4) The manufacturing method according to claim 1, wherein the degree of crosslinking of the crosslinked polyolefin polymer position is 10 to 60%.