JPH07179647A - Resin particle for production of flame retardant foam of good dimensional stability and its production - Google Patents

Abstract

PURPOSE:To produce a resin particles improved in flame retardancy, expandability, etc., by impregnating a product (SOP resin) obtained by grafting a styrene monomer onto an olefin resin with an aliphatic or alicyclic hydrocarbon having a boiling point lower than the softening point of the polymer and tetrabromocyclooctane(TBO). CONSTITUTION:An olefin resin (A) such as a polyethylene or an ethylene/vinyl acetate copolymer is dispersed in an aqueous medium comprising water or 0.01-5wt.%, based on the water, dispersant, 0.5-5 pts.wt. per pt.wt. component A containing a polymerization initiator, styrene monomer is added to this dispersion, a dicumyl peroxide crosslinking agent is optionally added to the mixture, and the entire is kept at 60-120 deg.C for 2-12hr to polymerize component C in particles of component A and further kept at 100-150 deg.C for 1-10hr to accomplish the grafting to obtain SOP resin particles. 100 pts.wt. SOP is mixed with 2-20 pts.wt. TBO and a hydrocarbon having a boiling point lower than the boiling point of SOP together with a small amount of a solvent and suspended in an aqueous medium under agitation, kept at 70-130 deg.C for 1hr or longer and cooled to obtain expandable particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing expandable resin particles, and in particular, expandable resin particles suitable for producing a flame-retardant foam having good dimensional stability and impact resistance. And a manufacturing method thereof.

[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 the foaming agent,
When it is contacted 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, which is widely used in the production of foams.

However, a foam made of expandable polystyrene particles has a drawback of being easily burned. Therefore, an attempt was made to make it flame-retardant. The attempt is to add a flame retardant to polystyrene to make the foam flame retardant, and various flame retardants have been proposed. However, in general, when a flame retardant is added, the fusion of particles becomes poor, the heat resistance of the foam becomes poor, and the dimensional stability becomes poor.

For example, Japanese Patent Application Laid-Open No. 3-124744 discloses a styrene resin particle having a melting point of 70 to 70 in order to make it flame-retardant.
The bromine-containing aromatic compound at 120 ° C. and tetrabromocyclooctane were used in a weight ratio of the former 2 to 90 to the latter 98.
It is proposed to mix them at a ratio of 10 to 10. However, when the bromine-containing aromatic compound is added as described above, the softening point of the resin is lowered, the expansion ratio is lowered, and the obtained foam has poor dimensional stability. Therefore, the expandable particles could not be satisfied in the fields where dimensional stability and heat resistance are required.

Further, Japanese Patent Application Laid-Open No. 3-124744 discloses that
Although the flame-retardant resin is widely described as a styrene resin, the substance is only a homopolymer and a very limited copolymer. That is, the copolymer is explained that it is possible to use a small amount of another monomer copolymerized with a styrene-based monomer, and as the other monomer, butadiene, methyl methacrylate, acrylonitrile, brominated styrene, Only maleic anhydride and itaconic acid are shown as examples. So
The teaching was merely to teach that the copolymer can be used by mixing the monomers with each other and copolymerizing them easily.

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 simply mixing and copolymerizing styrene and ethylene, but is obtained by absorbing styrene into already polymerized polyethylene and graft-polymerizing styrene onto polyethylene. . In addition, some styrene-modified polyethylene contains a large amount of ethylene therein. Therefore, styrene-modified polyethylene is different from the above-mentioned styrene resin.

It has already been proposed to make foams made using the above-mentioned styrene-modified polyethylene flame-retardant. 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 flame-retardant by maintaining the remaining amount of the foaming agent and the expansion ratio in a specific relationship. I just did it. 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 combustible foaming agent remaining in the molded body is X% by weight, X ² It is said that the foam becomes flame-retardant if it is adjusted so that Y ≦ 5. However, when 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 is not sufficient, although it is flame-retardant.

[0008]

SUMMARY OF THE INVENTION The present invention is intended to provide expandable particles which always produce a flame-retardant foam regardless of the expansion ratio regardless of the expansion ratio. . At the same time, the present invention intends to provide expandable particles which are easy to expand as expandable particles, and the foamed product obtained by foaming has excellent physical properties.

[0009]

The inventor of the present invention uses a copolymer of styrene instead of polystyrene, and includes a flame retardant and a foaming agent to produce expandable particles satisfying the above-mentioned requirements. I planned to do it.

The present inventor has prepared various copolymers of styrene, added various flame retardants to the composition to make compositions, and impregnated the compositions with various foaming agents to form expandable resin particles. It was Further, the present inventor made a foam by contacting the expandable particles thus produced with water vapor and heating them, and measured the foaming performance at that time and the physical properties of the obtained foam. As a result, the inventor has used a graft polymer obtained by graft-polymerizing a styrene-based monomer to a particle of polyethylene in a specific ratio, and also contains tetrabromocyclooctane as a flame retardant in a specific amount. If it is a composition and a foaming agent such as butane is included in such a composition,
It has been found that the desired expandable resin particles can be obtained. The present invention has been completed based on such knowledge.

The present invention is intended to provide the expandable particles as described above, and also to provide a method for producing the expandable particles as described above. Among them, the invention aiming to provide expandable particles is a graft polymer 100 obtained by graft-polymerizing 0.5 to 5 times by weight of styrene-based monomer with respect to 1 of olefin-based resin.
2 parts by weight or more of an aliphatic hydrocarbon or a cycloaliphatic hydrocarbon having a boiling point lower than the softening point of the graft polymer and 2 to 20 parts by weight of tetrabromocyclooctane are impregnated into the parts by weight. It is a feature.

In the invention relating to the method for producing expandable particles as described above, the olefin resin 1 has a weight ratio of 0.
Graft polymerization of 5 to 5 times the amount of the styrene monomer is carried out, 100 parts by weight of the obtained graft polymer particles are dispersed in an aqueous medium, and a fat having a boiling point lower than the softening point of the above graft polymer is added thereto. 2 parts by weight or more of group hydrocarbon or cycloaliphatic hydrocarbon, and tetrabromocyclooctane 2-20
70 parts by weight and 70 parts by weight while stirring in a closed container.
It is characterized in that it is kept at a temperature of 30 ° C. for 1 hour or more.

In the present invention, a graft polymer obtained by graft-polymerizing 0.5 to 5 times the amount of the styrene-based monomer with respect to the olefin-based resin 1 by weight as the resin (hereinafter, referred to as
This is called SOP). As this polymer,
Graft weight obtained by dispersing 100 parts by weight of olefin resin particles in an aqueous medium, adding 50 to 500 parts by weight of a styrene-based monomer thereto, and performing suspension polymerization in the presence of a polymerization initiator. It is preferable to use the coalesce 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-based monomer, styrene derivatives such as α-methylstyrene, vinyltoluene and chlorostyrene can be used in addition to styrene. As the styrene-based monomer, not only the styrene-based monomer, but also other monomers that can be copolymerized with the styrene-based monomer such as acrylonitrile and butyl acrylate, and the styrene-based monomer It is also possible to use mixtures.

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

In order to make 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 to the dispersion. As the polymerization initiator, those generally used when polymerizing a styrene-based monomer can be used. For example, benzoyl peroxide, t-butyl peroxybenzoate, etc. can be used. In addition, dicumyl peroxide can be used as a crosslinking agent.

In order to prepare the graft polymer, it is preferable to polymerize the styrene-based monomer so that it is uniformly absorbed by the olefin-based resin. Further, heating is carried out to accelerate the polymerization, but the temperature is preferably 60 to 120 ° C. The temperature is maintained at this temperature for 2 to 12 hours to polymerize the styrene monomer in the particles of the olefin resin. After that, further increase the temperature to complete the crosslinking 1
It is preferable to maintain the temperature of 00 to 150 ° C. for 1 to 10 hours.

Thus, SOP resin particles are obtained. These particles are grown using the olefin resin particles used at the beginning as cores. Therefore, in order to obtain fine SOP resin particles, it is necessary to use the olefin resin particles initially charged as fine particles.

In the present invention, tetrabromocyclooctane (hereinafter referred to as TBO) is used as a flame retardant in the SOP obtained as described above. TBO is known as a flame retardant. Further, as described above, TBO is known to be mixed with a bromine-containing aromatic compound having a special melting point in a specific ratio to be used for flame retarding expanded styrene resin particles. However, TBO has hitherto not been used for copolymers of olefins and styrene, especially for SOPs. Actually, TBO is SO
When used for P, it was surprisingly found that a bromine-containing aromatic compound, which has been required to be used at the same time, is unnecessary, and a foam obtained when the bromine-containing aromatic compound is expanded. Was found to have good dimensional stability.

In the present invention, in 100 parts by weight of SOP,
It is necessary to include 2 to 20 parts by weight of TBO.
The reason is that if the TBO content is less than 2 parts by weight, the composition obtained does not exhibit sufficient flame retardancy.
This is because if the amount exceeds 0 parts by weight, the dimensional stability of the foam will be poor when the obtained composition is foamed.

In the present invention, in order to make the particles of the composition composed of SOP and TBO expandable, a foaming agent is included therein. As the foaming agent, those which have been used so far for imparting foamability to the styrene resin can be used. The blowing agent is an aliphatic or cycloaliphatic hydrocarbon having a boiling point below the softening point of SOP. For example, propane, which belongs to the aliphatic hydrocarbon,
Examples thereof include isobutane, n-butane, pentane, and the like, and cyclopentane, cyclohexane, and the like belong to the cycloaliphatic hydrocarbon. 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 per 100 parts by weight of SOP. The reason why the amount is 2 parts by weight or more is that if the amount is less than 2 parts by weight, even if the SOP containing this is heated, it will not satisfactorily foam. This is because as the amount of the foaming agent contained increases, the foaming agent tends to foam at a high magnification, and when it exceeds a certain limit, it does not foam at a higher magnification beyond that, but no clear limit is observed in that limit. .

The TBO and the foaming agent are contained in the SOP by suspending them in an aqueous medium. First, a watertight container such as 100
Then, 100 parts by weight of SOP and then 2 to 20 parts by weight of TBO are added and well stirred, and these are suspended in an aqueous medium. Then, the container is closed and the foaming agent is pressed into the aqueous medium while stirring. At this time, when the foaming agent is in a liquid state, TBO may be dissolved in the foaming agent and the resulting solution may be pressed into the container. At this time, it is preferable to add a small amount of a solvent that dissolves the SOP to the container. As the solvent, for example, aromatic hydrocarbons such as benzene, toluene and xylene, and esters such as methyl acetate and ethyl acetate can be used. This solvent is composed of TBO and SO
It acts to promote absorption by P.

After the foaming agent is pressed into an aqueous medium in which SOP and TBO are suspended, the temperature of the aqueous medium is heated to 70 to 130 ° C. while stirring the aqueous medium, and this state is maintained for 1 hour. Continue above. Then cool and remove from container S
Take out the OP. What is taken out here is the expandable particles intended in the present invention.

In the above operation, the reason why the temperature inside the container, that is, the temperature of the aqueous medium is 70 to 130 ° C., comes from the results of experiments as described below. That is,
When the temperature in the container is lower than 70 ° C, the flame-retardant property of the expandable particles to be obtained is insufficient. This is because the cells of the granules are made fine and the fusion during foam molding is hindered, and the physical properties of the molded product deteriorate.

As mentioned above, an aqueous medium is placed in this using a closed container, and 100 parts by weight of S is added to the aqueous medium.
OP and 2 to 20 parts by weight of TBO are added, and 2 parts by weight or more of a foaming agent is pressed into the mixture, and the aqueous medium is mixed with 70% while stirring.
When heated to ~ 130 ° C and kept at this temperature for 1 hour or more, TBO and the foaming agent are uniformly impregnated in the SOP, and the SOP keeps the shape of the grain as it is, and the desired shape and size are obtained here. The following expandable particles are obtained. According to the method of the present invention, the expandable particles are thus easily obtained.

When the expandable particles thus obtained are brought into contact with steam and heated, the expandable particles are well expanded in proportion to the content of the foaming agent. After leaving the foamed particles at room temperature for several days, put them in a perforated mold for molding,
When steam is blown into the mold and heated, the particles are further foamed and fused to each other to form a foamed molded body.

In the foamed molded product thus obtained, the particles are strongly fused to each other in the foamed molded product, and the surface has a shape in close contact with the surface of the mold and has a size and shape as the mold. Further, this foamed molded article has a high impact resistance and is not easily broken even if a metal block is dropped on it. Also,
This molded body shows flame retardancy, and after igniting this, measuring the flame retardance by measuring the distance to continue burning,
Flame retardance is sufficient. What is more surprising is that the dimensional stability is high and the shrinkage after molding is small despite the addition of the flame retardant. Therefore, it is suitable for use as a structural material for transport boxes, automobile bumpers, door pads, etc. In this respect, the effect of the present invention is great.

Next, the effects of the present invention will be concretely clarified with reference to Examples and Comparative Examples. In the following, simply "parts" means "parts by weight". In addition, flame retardancy, bead bonding, dimensional stability of molded products, and impact resistance were measured in Examples and Comparative Examples, which were measured by the following methods. (A) Flame retardancy was determined by measuring the burning rate (length mm) for 1 minute by the method defined by FMVSS No. 302 (US automobile safety standard). 80 mm / min or less is considered good. (B) The bead bond represents the quality of the bond between the expanded particles in the expanded molded article. (C) The dimensional stability of the molded product is 70 ° C after the foam molding.
The rate of shrinkage when left to stand for 4 days was measured. (D) The impact resistance was considered to be fractured when a 321 g steel ball was dropped onto a foamed molded body having a size of 215 × 40 × 20 mm and a break having a length of 40 mm or more was generated,
The height at break was measured. (Based on JIS K6745)

[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, sodium dodecylbenzenesulfonate of 0.
Add 02 parts of the mixture, and add polyethylene resin particles (Sumitomo Chemical Co., Ltd., trade name Evatate D-1042) to the mixture.
30 parts was added, and the mixture was stirred at 250 rpm and suspended in an aqueous medium.

Separately, 0.3 part of benzoyl peroxide and 0.01 part of t-butyl peroxybenzoate were used as a polymerization catalyst, and 70 parts of styrene monomer of 0.25 part of dicumyl peroxide was used as a crosslinking agent. To prepare a monomer solution, which was added to the aqueous medium to be absorbed by polyethylene resin particles, and maintained at a temperature of 85 ° C. for 4 hours for polymerization. Then, the temperature was raised to 143 ° C., the temperature was maintained for 3 hours to complete the polymerization, and then the mixture was cooled to obtain SOP particles.

Next, 100 parts of water and 0.03 part of sodium dodecylbenzene sulfonate were put into an autoclave having an internal volume of 10 liters to prepare an aqueous medium, and 100 parts of the SOP particles obtained above were put therein. After stirring and dispersing, TBO (Daiichi Kogyo Seiyaku Co., Ltd., trade name F
2 parts of R 200) and 1.5 parts of toluene as a solvent were added and dispersed by stirring. Then, the autoclave was closed and 14 parts of butane as a foaming agent was press-fitted into this aqueous dispersion while continuing stirring. The aqueous dispersion was then heated to 125 ° C. and kept at this temperature for 3 hours with stirring to impregnate the SOP with the blowing agent. Then, it cooled and obtained the flame-retardant expandable particle. At this time, the particles retained their original shape, and no lumps were formed.

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 for 7 days at room temperature, 400 × 300 × 100 mm
In a molding die of the size
cm ² of water vapor was introduced for 1 minute and heated, then cooled for 20 minutes and the foamed molded product was taken out.

The foamed molded product obtained above was dried in a drying chamber at 50 ° C. for 3 hours.
After being dried for a day, a combustion test was conducted according to the method specified in FMVSS No. 302.
It was confirmed that, in mm / min, the flame retardance satisfying 80 mm / min or less was satisfied. Further, this foamed molded product had good moldability. Furthermore, about this foam molded article
When the shrinkage rate after being left at 4 ° C. for 4 days was examined, it was found that the shrinkage rate was 0.5%, which was small. The foamed article had a falling ball value of 35.5 cm and good impact resistance. Thus, this foamed molded product is not only flame-retardant, but also has high impact resistance, good dimensional stability, easy foam molding, and a good appearance, so that it has a structure similar to that of automobile bumpers and door pads. It was confirmed to be suitable for use as a material.

[0036]

[Examples 2 to 5] Examples 2 to 5 were carried out in the same manner as Example 1, except that the amount of TBO used was changed to 5, 5, 10 and 20 parts per 100 parts of SOP, respectively.
The temperature at which the foaming agent was impregnated in the autoclave was maintained at 120 ° C, 100 ° C, 70 ° C, and 70 ° C, respectively, and flame-retardant expandable particles were obtained.

Using the expandable particles thus obtained, a foamed molded product was produced in exactly the same manner as in Example 1. When the properties of this foamed molded product were investigated, it was found that FMVSS No. 302
In the flame retardancy test of No. 3, the combustion speeds of 60, 70, 70 and 61 mm / min were shown, and thus it was determined that the flame retardancy was good. Moldability is good, dimensional stability is good, and falling ball values are 41.5 and 3 respectively.
It was 8.5, 38.5, and 36.5 cm, and had high impact resistance. Therefore, it was recognized that it gave a good foam.

[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 to carry out the treatment outside the range specified by the present invention.

More specifically, in Comparative Example 1, the amount of TBO used was 1.5 parts and the impregnation temperature was 135 ° C.
In Comparative Example 2, the amount of TBO used was 25 parts and the impregnation temperature was 6
The temperature is 5 ° C., and 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 expandable particles were treated in exactly the same manner as in Example 1 to produce a foamed molded product. The physical properties of this foamed molded product were examined in exactly the same manner as in Example 1. The results will be described in order of Comparative Examples 1 to 3, FMVS.
In the flame retardancy test of S No. 302, the burning rate was 8 each
No flame retardancy was observed at 2, 68 and 210 mm / min, and the moldability was poor in Comparative Example 1, but Comparative Examples 2 and 3
And Comparative Example 3 had good dimensional stability, but Comparative Examples 1 and 2 had poor dimensional stability, and the falling ball values were 20.5, 38.5,
At 26.5 cm, Comparative Example 2 was 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 thereof was 5 parts per 100 parts of SOP. The impregnation temperature of the foaming agent was 120 ° C.

More specifically, in Comparative Example 4, tribromophenyl allyl ether was used as a flame retardant, in Comparative Example 5, tetrabromobisphenol A bisallyl ether was used, and in Comparative Example 6, tetrabromobisphenol A dibropropyl. Ether was used, hexabromocyclododecane was used in Comparative Example 7, decabromodiphenyl ether was used in Comparative Example 8, and chlorinated paraffin was used in Comparative Example 9, both of which were 5 parts per 100 parts of SOP and 120 ° C. With a foaming agent, otherwise in Example 1
Flame retardant expandable particles were obtained in the same manner as in.

The expandable particles thus obtained were treated in exactly the same manner as in Example 1 to prepare a foamed molded product. The physical properties of this foamed molded product were examined in exactly the same manner as in Example 1. The results will be described in order of Comparative Examples 4 to 9. FMVSS No. 3
In the 02 flame retardancy test, the burning rates were 100 and 9 respectively.
5, 110, 98, 116, 125 mm / min for all 8
The standard of 0 mm / min was not reached. The moldability was good except for Comparative Example 9, but the dimensional stability was Comparative Example 4,
Comparative examples 5 to 7 were good with 8 and 9 being bad, and falling ball values of 31.5, 36.5, 23.5, 19.5 and 2, respectively.
At 2.5 and 16.5, Comparative Examples 4 and 5 were good, but Comparative Examples 6 to 9 were all bad.

Table 1 below shows the results of Examples 1 to 5 and Comparative Examples 1 to 9 described above.

[0045]

[Table 1]

Claims (2)

[Claims] 1. A weight ratio of 0.5 to 1 of the olefin resin.
To 100 parts by weight of a graft polymer obtained by graft-polymerizing a styrene-based monomer in an amount of up to 5 times, an aliphatic hydrocarbon or a cycloaliphatic hydrocarbon having a boiling point lower than the softening point of the graft polymer 2 Characterized by being impregnated with at least 2 parts by weight of tetrabromocyclooctane and 2 parts by weight of tetrabromocyclooctane,
Resin particles for producing flame-retardant foam having good dimensional stability. 2. The weight is 0.5 with respect to 1 of the olefin resin.
~ 5 times the amount of the styrene-based monomer is graft-polymerized, 100 parts by weight of the resulting graft polymer particles are dispersed in an aqueous medium, and an aliphatic compound having a boiling point lower than the softening point of the graft polymer is added thereto. 2 hydrocarbons or cycloaliphatic hydrocarbons
70 parts by weight or more and 2 to 20 parts by weight of tetrabromocyclooctane are added, and the mixture is stirred in a closed container while stirring 70 to 13
A method for producing resin particles for producing a flame-retardant foam having good dimensional stability, which is characterized by holding at a temperature of 0 ° C. for 1 hour or more.