JP3093551B2 - Resin particles for producing flame-retardant foam having good dimensional stability and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable resin particles, and more particularly to expandable particles suitable for producing a flame-retardant foam having good dimensional stability and high impact resistance, and production thereof. It is about the method.

[0002]

2. Description of the Related Art As expandable resin particles, those using polystyrene as a resin are known. Expandable particles made of polystyrene have good retention of foaming agent,
When it is brought into contact with water vapor, it is easily foamed at a high magnification, and the particles are strongly fused to each other to give a good foam. Therefore, it is widely used in the production of foam.

[0003] However, foams made from polystyrene expandable particles have the disadvantage that they are easily burned. Therefore, an attempt was made to make this flame-retardant. The attempt was to add a flame retardant to polystyrene to make the foam flame retardant. However, when a flame retardant is added, the fusion of particles is generally deteriorated, the heat resistance of the foam is deteriorated, and the dimensional stability is deteriorated.

[0004] For example, Japanese Patent Application Laid-Open No. 3-124744 discloses a method for making styrene resin particles flame-retardant.
A bromine-containing aromatic compound at 120 ° C. and tetrabromocyclooctane in a weight ratio of the former 2-90 to the latter 98 were used.
It has been proposed to use a mixture in a ratio of 10 to 10. However, when the bromine-containing aromatic compound is added in this manner, the softening point of the resin decreases, the expansion ratio decreases, and the obtained foam has poor dimensional stability. Therefore, these expandable particles cannot be satisfactory in the field where dimensional stability and heat resistance are required.

In Japanese Patent Application Laid-Open No. 3-124744, a resin which can be used for flame retardation is described as a styrene resin, but the substance is mainly a homopolymer such as styrene or α-methylstyrene. I was It states that in addition to homopolymers, styrene copolymers containing small amounts of other monomers can also be used, but other monomers include butadiene, methyl methacrylate, acrylonitrile, and bromine. Styrene, maleic anhydride and itaconic acid were merely examples. Therefore, it was only said that a copolymer capable of mixing and copolymerizing monomers could be used.

On the other hand, it has been known to use styrene-modified polyethylene as expandable particles instead of polystyrene. Styrene-modified polyethylene is not obtained by mixing and copolymerizing styrene and ethylene,
It is obtained by absorbing styrene into already polymerized polyethylene and graft-polymerizing styrene onto polyethylene. Further, some styrene-modified polyethylenes contain a large amount of ethylene therein. Therefore, the styrene-modified polyethylene is different from the styrene-based resin described above.

[0007] It has already been proposed to flame retard foams made using the styrene-modified polyethylene described above. It is described in Japanese Patent Application No. 4-107297. However, this flame-retardant styrene-modified polyethylene foam does not use a flame retardant, but maintains the foaming agent residual amount and the expansion ratio in a specific relationship to make the foam flame-retardant. It just did. That is, in the case of a styrene-modified polyethylene foam having a molding multiple of 35 times or less, where the molding multiple is Y times and the amount of the flammable blowing agent remaining in the molded body is X% by weight, X ² · Y It is said that when adjusted so as to be ≦ 5, the foam becomes flame-retardant. However, if the molding multiple exceeds 35 times, the foam does not become flame-retardant even if X and Y satisfy the above formula. Therefore, this flame-retardant styrene-modified polyethylene foam was not satisfactory even though it was flame-retardant.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a foamable particle which exhibits satisfactory flame retardancy regardless of the expansion ratio when foamed particles are made flame retardant and foamed. It is intended to provide. At the same time, the present invention seeks to provide expandable particles that can be easily expanded as expandable particles, and that a foam obtained by expansion has excellent physical properties.

[0009]

Means for Solving the Problems The present inventor uses a styrene copolymer instead of polystyrene and includes a flame retardant and a foaming agent to produce foamable particles satisfying the above requirements. I tried to do it.

The inventor of the present invention made various copolymers of styrene, added various flame retardants to the compositions to form compositions, and impregnated the compositions with various blowing agents to form expandable resin particles. Was. Further, the inventor made a foam by bringing steam into contact with the foamable particles thus obtained, and measured the foaming performance and physical properties of the foam at that time. As a result, the present inventor used a graft polymer obtained by graft-polymerizing a styrene-based monomer to a polyethylene particle at a specific ratio, and also contained a specific amount of tetrabromocyclooctane as a flame retardant. It has been found that it is better to make a composition. It has been found that using such a composition, expandable resin particles satisfying the above-mentioned requirements can be obtained only by adding a blowing agent such as butane according to a conventional method. The present invention has been completed based on such knowledge.

The present invention includes an invention of expandable particles and an invention of a method for producing the expandable particles. Among them, the invention of the expandable particles is based on the fact that tetrabromocyclo is added to 100 parts by weight of a graft polymer obtained by graft-polymerizing a styrene-based monomer in an amount of 0.5 to 5 times the weight of the olefin-based resin 1 by weight. 5 to 20 parts by weight of octane and 2 or more parts by weight of an aliphatic or cycloaliphatic hydrocarbon having a boiling point lower than the softening point of the graft polymer.

Further, the invention relating to the production method is characterized in that a styrene-based monomer is graft-polymerized in an amount of 0.5 to 5 times the weight of the olefin-based resin 1 and 100 parts by weight of the obtained graft polymer particles are pressure-tightly sealed. Into a rotary mixer of the type, and at least 2 parts by weight of an aliphatic hydrocarbon or a cycloaliphatic hydrocarbon having a boiling point lower than the softening point of the graft polymer,
5 to 20 parts by weight of tetrabromocyclooctane,
The method is characterized in that the rotary mixer is maintained at a temperature of 70 to 85 ° C. for 1 hour or more while being rotated while being sealed.

In the present invention, a graft polymer (hereinafter, referred to as a resin) obtained by graft-polymerizing a styrene-based monomer in an amount of 0.5 to 5 times the weight of the olefin-based resin 1 as a resin.
This is called SOP). To make this polymer, 100 parts by weight of olefin resin particles are dispersed in an aqueous medium, 50 to 500 parts by weight of a styrene monomer is added thereto, and suspension polymerization is performed in the presence of a polymerization initiator. The obtained graft polymer is preferably used as it is in the form of particles.

As the above-mentioned olefin resin, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer and the like can be used.

As the above-mentioned styrene monomer, styrene derivatives such as α-methylstyrene, vinyltoluene and chlorostyrene can be used in addition to styrene. In addition, styrene-based monomers include not only styrene-based monomers but also other monomers that can be copolymerized with styrene-based monomers such as acrylonitrile and butyl acrylate, and styrene-based monomers. It may contain a mixture.

The aqueous medium used for the graft polymerization comprises water and an appropriate amount of a dispersant. Examples of dispersants include organic compounds such as partially saponified polyvinyl alcohol, polyacrylate, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, calcium stearate, ethylenebisstearamide, calcium pyrophosphate, calcium phosphate, calcium carbonate, and magnesium carbonate. , Magnesium phosphate, magnesium pyrophosphate, magnesium oxide, and other inorganic compounds composed of fine powders that are hardly soluble in water can be used. In the present invention, when an inorganic compound is used as a dispersant, it is preferable to use a surfactant such as sodium dodecylbenzenesulfonate in combination. These dispersants are generally present in water at a concentration of 0.
It is used by adding 01 to 5% by weight.

In order to produce a graft polymer, it is necessary to disperse the above-mentioned olefin resin particles in an aqueous medium and add a styrene monomer containing a polymerization initiator thereto. As the polymerization initiator, those generally used for polymerizing a styrene monomer can be used. For example, benzoyl peroxide, t-butyl peroxybenzoate, and the like can be used. In addition, dicumyl peroxide can be used as a crosslinking agent.

In order to prepare a graft polymer, it is preferable to polymerize the styrene monomer so that the styrene monomer is uniformly absorbed by the olefin resin. Heating is performed to promote polymerization, and the temperature is preferably set to 60 to 120 ° C. This temperature is maintained for 2 to 12 hours to polymerize the styrene monomer in the olefin resin particles. Thereafter, in order to complete the crosslinking, the temperature was further increased to 100
It is preferred to maintain the temperature at ~ 150 ° C for 1-10 hours.

Thus, SOP resin particles are obtained. These particles are grown with the olefin resin particles used first as nuclei. Therefore, in order to obtain fine SOP resin particles, it is necessary to use olefin-based resin particles to be initially charged as fine particles.

In the present invention, tetrabromocyclooctane (hereinafter referred to as TBO) is used for the SOP obtained as described above. TBO is known as a flame retardant. Further, as described above, TBO is mixed with a bromine-containing aromatic compound having a special melting point in a specific ratio,
It has been used for flame retarding expanded styrenic resin particles. However, TBO has not yet been used for copolymers of olefins and styrene, especially SOPs.
In fact, it has been found that when TBO is used for an SOP, the bromine-containing aromatic compound which has been required to be used in combination is surprisingly unnecessary, and the SOP can be made flame-retardant using TBO alone.

According to the present invention, 100 parts by weight of SOP
It is necessary to include 5 to 20 parts by weight of TBO.
The reason is that if the TBO is less than 5 parts by weight, the obtained composition does not show sufficient flame retardancy.
If the amount exceeds 0 parts by weight, the dimensional stability of the foamed product when the obtained composition is foamed becomes poor.

In the present invention, in order to make the particles of the composition comprising SOP and TBO foamable, a foaming agent is added to the particles. As the foaming agent, those which have been used so far for imparting foamability to the styrenic resin can be used. The blowing agent is an aliphatic or cycloaliphatic hydrocarbon having a boiling point below the softening point of the SOP. For example,
Aliphatic hydrocarbons include propane, isobutane, n-butane, pentane and the like, and cycloaliphatic hydrocarbons include cyclopentane and cyclohexane. These can be used alone or in combination.

In the present invention, the foaming agent is contained in an amount of 2 parts by weight or more based on 100 parts by weight of the SOP. The reason for setting the content to 2 parts by weight or more is that if the content is less than 2 parts by weight, the SOP containing the SOP will not be foamed satisfactorily even when heated. In addition, the reason that no particular upper limit is set for the amount of the foaming agent is that as the amount of the foaming agent increases, it tends to foam at a high magnification, and when it exceeds a certain limit, it does not foam at a higher magnification any more. This is because no limit is recognized.

In order to include TBO and a foaming agent in the SOP, a pressure-resistant hermetic rotary mixer is used. First, 100 parts by weight of SOP is put into this mixer, and then 5 to 20 parts by weight.
Add parts by weight of TBO and 2 parts by weight or more of blowing agent and seal the mixer. At this time, after the TBO is put in first and the mixer is rotated and well stirred, a foaming agent may be added,
When the foaming agent is in a liquid state, TBO may be dissolved in the foaming agent, and the resulting solution may be placed in a mixer. Also,
At this time, it is preferable to add a small amount of a solvent that dissolves the SOP into the mixer. The solvent is, for example, an aromatic hydrocarbon such as benzene, toluene or xylene, or an ester such as methyl acetate or ethyl acetate. This solvent serves to promote the impregnation of the SOP with TBO and the blowing agent.

The SOP, TBO, and blowing agent are put into a mixer, sealed, and then the mixer is rotated. While continuing to spin, heat the mixer to a temperature of 70-85 ° C. This rotation and heating are continued for one hour or more. After cooling, the SOP is removed from the mixer. What was taken out here,
The foamable particles according to the present invention.

In the above operation, the temperature of the mixer was set to 70
The reason for setting the temperature to 〜85 ° C. comes from the results of experiments described below. That is, when the temperature of the mixer is lower than 70 ° C., the flame retardancy of the obtained expandable particles is insufficient, and when it is higher than 85 ° C., the expandable particles obtained fuse together to form aggregates. This is because, when this is foamed, it becomes a large mass like a golf ball, and the subsequent molding cannot be performed smoothly.

As described above, 100 parts by weight of SOP, 5 to 20 parts by weight of TBO and 2 parts by weight or more of a foaming agent are put into a pressure-resistant hermetic rotary mixer, and the mixer is rotated. When maintained at a temperature of 70 to 85 ° C. for 1 hour or more, the TBO and the foaming agent are uniformly impregnated in the SOP, and the SOP maintains the shape of the granules as they are, and has a desired shape and size. Expandable particles are easily obtained. The method of the present invention thus offers the advantage that the production of expandable particles is easy.

When the expandable particles thus obtained are heated while being brought into contact with water vapor, they expand at a high magnification in proportion to the content of the blowing agent. After leaving the foamed particles at room temperature for several days, put them into a perforated mold for molding,
When water vapor is blown into the mold and heated, the particles are further foamed and fused together to form a foamed molded article.

In this foam molded article, the particles are strongly fused to each other therein, and the surface thereof has a shape closely adhered to the surface of the mold, and has a size and shape corresponding to the mold. Further, this foam molded article has high impact resistance, and is not easily broken even if a metal lump is dropped thereon. In addition, this molded article exhibits flame retardancy, and the flame retardancy is sufficient if the flame retardancy is measured by measuring the distance of continuing burning after ignition. What is more surprising is that despite the addition of the flame retardant, the dimensional stability is large and the shrinkage after molding is small. Therefore, it is suitable for use as a structural material for transport boxes, automobile bumpers, door pads, and the like. In this respect, the effect of the present invention is great.

Next, the effects of the present invention will be specifically described with reference to examples and comparative examples. In the following, simply “parts” refers to parts by weight. In Examples and Comparative Examples, flame retardancy, bead bonding, dimensional stability of molded articles, and impact resistance were measured by the following methods. (A) Flame retardancy is determined by a method defined by FMVSS 302 (U.S.A.
m) was measured. 80 mm / min or less is considered good. (B) Bead bonding indicates the quality of the bonding between the foamed particles in the foamed molded article. (C) For the dimensional stability of the molded product, 70
The shrinkage ratio when left at 4 ° C. for 4 days was measured. (D) The impact resistance was considered to have been broken when a steel ball of 321 g was dropped on a foamed molded article having a size of 215 × 40 × 20 mm to form a cut having a length of 40 mm or more.
The height at break was measured. (Based on JIS-K 6745)

[0031]

Example 1 In an autoclave having an internal volume of 100 liters, 100 parts of pure water as an aqueous medium, 0.45 part of magnesium pyrophosphate, 0.1% of sodium dodecylbenzenesulfonate.
02 parts of the mixture was added, and polyethylene resin particles (trade name: Evatate D-1042, manufactured by Sumitomo Chemical Co., Ltd.) were added thereto.
30 parts were added, and the mixture was stirred at a rotation speed of 250 rpm and suspended in an aqueous medium.

Separately, 0.3 part of benzoyl peroxide and 0.01 part of t-butylperoxybenzoate as a polymerization catalyst, and 0.25 part of dicumyl peroxide as a crosslinking agent are added to 70 parts of a styrene monomer. To prepare a monomer solution, and this solution was added to the aqueous medium, absorbed by polyethylene resin particles, and kept at a temperature of 85 ° C. for 4 hours to carry out polymerization. Thereafter, the temperature was raised to 143 ° C. and maintained at this temperature for 3 hours to complete the polymerization, and then cooled to obtain SOP particles.

Next, 100 parts of the above-mentioned SOP particles were put into a pressure-resistant hermetic rotary mixer having an inner volume of 40 liters, and TBO (trade name: FR, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as a flame retardant.
200) 10 parts were charged and the mixer was rotated. Then, while rotating the mixer, toluene 1.5 as a solvent was used.
And 14 parts of butane as a blowing agent were sequentially press-fitted. Further, the mixture was mixed at a temperature of 70 ° C. for 3 hours while rotating the mixer to impregnate the foaming agent. Then, it cooled and flame-retardant expandable particles were obtained. At this time, the particles retained their original shape, and there were no agglomerates.

Thereafter, the flame-retardant expandable particles obtained above were pre-expanded at a bulk ratio of 55 times. After leaving the obtained pre-expanded particles at room temperature for 7 days, 400 × 300 × 100 mm
Into a molding die of the size of
The steam cm ² and heated by introducing 1 minutes, the expanded molded article then cooled for 20 minutes.

The foamed molding obtained above was dried in a drying chamber at 50 ° C. for 3 hours.
After drying for days, a combustion test was performed according to the method specified in FMVSS No. 302.
It was confirmed that the composition exhibited flame retardancy of 80 mm / min or less at a rate of mm / min. In addition, this foam molded article had good binding of beads. Further, when this foamed molded product was left at 70 ° C. for 4 days to examine the shrinkage, it was found that the shrinkage was 0.5%, which was small. Also,
The falling ball value of this foam molded product was 35.5 cm, and the impact resistance was good. Thus, since this foam molded article is not only flame-retardant, but also rich in impact resistance and good in dimensional stability, foam molding is easy and the appearance is good,
It has been confirmed that it is suitable for use as a structural material such as bumpers and door pads for automobiles.

[0036]

Embodiments 2 to 5 Embodiments 2 to 5 were carried out in the same manner as in Embodiment 1, except that the amount of TBO used was set to 5, 10, 15, and 20 parts for 100 parts of SOP, respectively. 85 ° C, 85 ° C, 70 ° C, and 70 ° C, respectively, when impregnating the foaming agent in the closed type rotary mixer.
, And flame retardant foamable particles were obtained in each case.

Using the obtained expandable particles, a foam molded article was produced in exactly the same manner as in Example 1. When the properties of this foamed molded product were examined, FMVSS No. 302
In the flame-retardant test of No. 6, the combustion speed was 80, 60, 69, and 65 mm / min. Each of the beads was in a good condition, the dimensional stability was good, and the falling ball value was 3
It was 4.5, 40.5, 37.5, 38.5 cm, and was rich in impact resistance. Therefore, it was recognized that a good foam was provided.

[0038]

Comparative Examples 1 to 3 This comparative example was carried out in the same manner as in Example 1, except that the amount of TBO used as a flame retardant was increased or decreased.
Further, the impregnation temperature of the foaming agent was changed so as to be out of the range specified by the present invention.

More specifically, in Comparative Example 1, the amount of TBO used was 4 parts and the impregnation temperature was 90 ° C., and in Comparative Example 2, the amount of TBO was 25 parts and the impregnation temperature was 65 ° C. Comparative Example 3 is a case where the amount of TBO used is zero and the impregnation temperature is 70 ° C.

The obtained flame-retardant foamable particles were treated in exactly the same manner as in Example 1 to produce a foam molded article. The physical properties of this foam molded article were examined in exactly the same manner as in Example 1. The results are described in the order of Comparative Examples 1 to 3, and FMVS
In the flame retardancy test of S No. 302, the burning speed was 8
At 4, 86 and 215 mm / min, none of the flame retardants were recognized, and the state of the beads was poor in Comparative Example 1 but in Comparative Example 2.
And 3 were good, and the dimensional stability was good in Comparative Examples 1 and 3, but Comparative Example 2 was bad, and the falling ball values were 32.5 and 3
At 0.5 and 26.5 cm, Comparative Examples 1 and 2 were better than Comparative Example 3 without the flame retardant. However, it was recognized that it was inferior to Examples 1 to 5 as a whole.

[0041]

Comparative Examples 4 to 9 This comparative example was carried out in the same manner as in Example 1, except that a flame retardant other than TBO specified in the present invention was used as the flame retardant, and the amount was 10 parts per 100 parts of SOP.
And the impregnation temperature of the foaming agent was 80 ° C.

More specifically, in Comparative Example 4, tribromophenylallyl ether was used as a flame retardant, in Comparative Example 5, bisallyl ether of tetrabromobisphenol A was used, and in Comparative Example 6, bisdibromopropyl of tetrabromobisphenol A was used. Comparative Example 7 used hexabromocyclododecane, Comparative Example 8 used decabromodiphenyl ether, Comparative Example 9 used chlorinated paraffin, and the amount was 1 to 100 parts of SOP.
0 parts, impregnated with a foaming agent at 80 ° C., and the other conditions were the same as in Example 1 to obtain flame-retardant foamable particles.

The obtained expandable particles were treated in exactly the same manner as in Example 1 to produce an expanded molded article. The physical properties of this foam molded article were examined in exactly the same manner as in Example 1. When the results are described in the order of Comparative Examples 4 to 9, FMVSS No. 3
02, the burning rates were 105, 10 and 10, respectively.
At 1, 118, 102, 122 and 130 mm / min, none of them reached the standard of 80 mm / min. The bead binding was all good, but the dimensional stability was poor in Comparative Examples 4, 8, and 9 and good in Comparative Examples 5 to 7, and the falling ball value was 2 for each.
9.5, 35.5, 23.5, 21.5, 20.5, 1
At 8.5, Comparative Examples 4 and 5 were good, but Comparative Examples 6 to
Nine were all bad.

The results of Examples 1 to 5 and Comparative Examples 1 to 9 are shown in Table 1 below.

[0045]

[Table 1]

Claims (1)

(57) [Claims] (1) 0.5 parts by weight based on 1 olefin resin.
Graft polymerization of about 5 times the amount of styrene monomer
100 parts by weight of the graft polymer particles thus obtained
Into the invert mixer, and add the softening point of the graft polymer
Aliphatic or cycloaliphatic hydrocarbons with lower boiling points
Hydrogen at least 2 parts by weight, tetrabromocyclooctane 5
~ 20 parts by weight, and the rotary mixer is closed and rotated.
While maintaining the temperature at 70-85 ° C for 1 hour or more
Characteristic resin with good dimensional stability and flame retardant foam production
Method for producing particles.