JP3348575B2 - Expandable rubber-modified styrenic resin particles, expanded resin particles and expanded molded article obtained using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a foamable rubber-modified styrene-based styrene-based material for obtaining foamed particles which can be molded in a short molding cycle and are suitable for foamed molded articles having excellent appearance, impact resistance and flexibility. The present invention relates to resin particles, expanded particles made of the particles, and expanded molded articles.

[0002]

2. Description of the Related Art Foams made of polystyrene resin have excellent cushioning properties and heat insulation properties and are easy to mold. Therefore, they are widely used as packaging materials and heat insulation materials. There is a problem that, for example, it is not suitable for packaging of precision instrument products, because of insufficient insufficiency and flexibility and chipping easily. On the other hand, foams made of polyolefin-based resin are foams with excellent impact resistance and flexibility, but require extensive equipment and are molded and processed by manufacturers in the form of foamed particles due to the nature of the resin. There is a problem that the production cost increases because the product must be transported to the manufacturer.

In recent years, a rubber-modified styrene resin foam has been disclosed in Japanese Patent Application Laid-Open No. 3-182 as one which is easy to mold and has improved impact resistance and flexibility over polystyrene resin foam.
No. 529 and JP-A-5-116227, however, the degree of improvement in impact resistance and flexibility was insufficient.

As a method for compensating for this, the present inventors have proposed the use of a rubber-modified styrene resin containing butadiene rubber having a high proportion of 1,4-cis structure (JP-A-7-90105). In the foamable resin particles using butane, which is known to be excellent in moldability as a foaming agent, in these resins, the bubbles of the foamed particles after heating and foaming become fine, and the molding obtained by using the same is used. Since the problem that the appearance of the product is deteriorated occurs, butane cannot be used as a main component of the foaming agent, and it is necessary to use n-pentane which does not make bubbles so small. However, when n-pentane is used as a foaming agent, the foamed particles are filled in a mold, and the cooling time during heat molding is relatively long, and the appearance of the molded product is improved, but in order to further increase the productivity, There was a limit.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the rubber-modified styrenic resin is composed of a specific rubber component and a styrenic resin; By limiting the mineral oil content in the resin, keeping the internal moisture content to 0.2% by weight or less, and using the foaming agent main component as butane, molding can be performed in a short molding cycle, and the appearance of the molded product and impact resistance The present inventors have found that expandable rubber-modified styrene resin particles for obtaining expanded resin particles that give expanded molded articles having excellent flexibility can be obtained, and have completed the present invention.

That is, the present invention contains 8 to 15% by weight of a butadiene rubber having a 1,4-cis structure ratio of 70% or more, the butadiene rubber is particulate, and the average particle size of the particles is A rubber-modified styrene resin comprising a rubber component having a size of 1.5 to 3.0 μm and a styrene resin, wherein the rubber component is dispersed in the styrene resin, wherein the mineral oil content in the resin is 3 A foamable rubber-modified styrene-based styrene-based resin, characterized in that the foamable rubber-modified styrene-based styrene-based styrene-based styrene-based material has a volatile foaming agent containing butane as a main component in an amount of 1 to 15 wt%. Resin particles.

[0007] The foamable rubber-modified styrene resin particles preferably contain cyclohexane. The styrene resin preferably has a Z-average molecular weight of 350,000 or more. The present invention also provides rubber-modified styrenic foamed resin particles obtained by heating and foaming the expandable rubber-modified styrenic resin particles according to claim 1. The present invention still further provides a foamed rubber-modified styrene-based resin molded article comprising the foamed rubber-modified styrene-based resin particles according to claim 4 having a density of 10 to 600 kg / m ³ .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The expandable rubber-modified styrene resin particles of the present invention contain 8 to 15% by weight of a butadiene rubber having a 1,4-cis structure ratio of 70% or more, and the butadiene rubber is in a particulate form. And the average particle size of the particles is 1.5
The rubber component is composed of a rubber component having a size of about 3.0 μm and a styrene resin, and the rubber component is a rubber-modified styrene resin obtained by dispersing the rubber component in the styrene resin.

The rubber component in the rubber-modified styrene resin of the expandable rubber-modified styrene resin particles of the present invention is 1,4-
When a rubber-modified styrene resin containing butadiene rubber having a cis structure ratio of 70% or more, preferably 90% or more and containing a low ratio of 1,4-cis structure is used, flexibility and impact resistance are reduced. Performance becomes insufficient. 1,4
Butadiene rubber having a cis structure ratio of 70% or more is, for example, a rare earth metal (atomic numbers 21, 39, 57 to 6).
2) a system catalyst, preferably a cerium group (atomic numbers 57 to 6)
2) It is obtained by performing coordination ion polymerization of butadiene in the presence of a system catalyst. The basic structure of a rare earth metal catalyst is
(A) a rare earth metal compound represented by the general formula MR ₃ (M is a rare earth metal and R is a reaction residue of an organic acid); (b)
It consists of an organoaluminum compound and (c) a halogen compound. The organic acid constituting the rare earth metal compound is, for example, an organic compound having an active hydrogen which can be substituted for a rare earth metal such as carboxylic acid, alcohol, and amine. (JP-A-55-66903 and JP-A-60-23)
Incidentally, the ratio of the cis structure in the present invention can be determined by measurement of ¹³ C-NMR spectrum or infrared absorption spectrum (Morler).
o) can be determined by the measurement.

In the present invention, those having a butadiene rubber content of 8 to 15% by weight, preferably 10 to 13% by weight, more preferably 11 to 13% by weight are used. When the amount is too small, sufficient flexibility and impact resistance cannot be obtained.On the contrary, when the amount is too large, the strength cannot be improved in proportion to the usage ratio.In addition, when a foam is produced using expanded particles obtained therefrom. In addition, moldability such as melting of the surface of the molded article is significantly deteriorated.

In the present invention, these butadiene rubbers have an average particle size of 1.5 to 3.0 μm, preferably 2.0 to 3.0 μm.
２2.8 μm. If it is less than 1.5 μm, the impact strength is insufficient, and if it is more than 3.0 μm, when these particles are foamed, stable bubble formation is not performed and problems such as easy shrinkage occur. The average particle size depends on factors such as the shape of the stirrer in the polymerization tank for styrene polymerization, the number of rotations of the stirrer, the stirring time, and the polymerization temperature. The range of the present invention can be achieved by changing such conditions, for example, by changing the rotational speed of the stirring.

The average particle size of the dispersed particles of butadiene rubber in the present invention is as follows:
It is a value obtained by measuring the particle diameter of 100 to 200 rubber particles and calculating by the following equation.

Average particle size = ΣNiD ² / ΣNiD (where Ni is the number of rubber particles and D is the particle size of the rubber particles.) In the rubber-modified styrene resin of the expandable rubber-modified styrene resin particles of the present invention. The styrene-based resin has a Z-average molecular weight of preferably 350,000 or more, more preferably 400,000 or more. Z average molecular weight of 350,
If it is smaller than 000, the resulting foam tends to have poor impact strength and flexibility.

The foamable rubber-modified styrene resin particles of the present invention have a mineral oil content of 3.0% by weight or less, preferably 2.0% by weight or less, and an internal water content of 0 in the rubber-modified styrene-based resin. 0.2% by weight or less, preferably 0.1% by weight or less, and 1 to 15% by weight, preferably 3 to 10% by weight of a volatile blowing agent described below. When the proportion of the mineral oil content in the particles of the present invention exceeds 3.0% by weight, the foam obtained using the same tends to shrink or deform.

The ratio of the amount of internal water in the particles of the present invention is
If the content exceeds 0.2% by weight, the cell size of the expanded particles becomes small, and the surface tends to melt or shrink at the time of molding, and the appearance of the molded product deteriorates.

The volatile foaming agent is mainly composed of butane which is a hydrocarbon compound having 4 carbon atoms such as n-butane and i-butane, that is, 50% by weight or more of the total volatile foaming agent. Industrially, it can be obtained as a mixture having a composition ratio of about 70% n-butane and about 30% i-butane. Also, propane, n-pentane, i-pentane, neopentane, cyclopentane, hexane, trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoroethane,
An organic compound having a boiling point of 80 ° C. or less such as chloromethane, chloroethane, dichloromethane, methanol, and diethyl ether can be mixed with butane and used as a foaming agent. The volatile foaming agent is usually supplied in such an amount that the foaming agent content in the produced polymer particles becomes 1 to 15% by weight.

The foaming property can be enhanced by adding a non-volatile plasticizer or a solvent such as volatile cyclohexane, xylene, or toluene, particularly at a ratio of 1% by weight or less. It is preferable from the viewpoint of properties. It is not preferable to add these plasticizers and solvents in an amount exceeding 1% by weight, since the cooling time during molding becomes longer and the intended object of the present invention may not be obtained.

The rubber-modified styrene resin used in the present invention is obtained by converting the above-mentioned specific butadiene rubber to styrene, p
-Risk polymerization and bulk polymerization in the presence of azo compounds such as azobis i-butyronitrile or peroxides such as benzoyl peroxide and t-butylperoxybenzoate by dissolving in styrene monomers such as -methylstyrene and α-methylstyrene. , Solution polymerization, suspension polymerization or bulk-suspension polymerization.

Further, rubber-modified styrene resins include inorganic fillers such as talc, clay, calcium carbonate and titanium oxide, antioxidants, antistatic agents, ultraviolet absorbers, carbon black, aluminum stearate, zinc stearate. , A lubricant such as pt-butyl aluminum benzoate, tris (dibromopropyl) phosphate, pentabromodiphenyl ether, tetrabromobutane, dibromoethylbenzol, 1,2,5,6,9,10-hexabromocyclodecane, etc. A flame retardant may be contained.

As a method for obtaining the foamable rubber-modified styrenic resin of the present invention, for example, melt kneading with an extruder, and a method of strand cutting, underwater cutting, hot cutting or the like to reduce the size to 0.5 to 5 mm. The granulated rubber-modified styrene resin particles are dispersed in an aqueous medium in a closed container in the presence of a suspending agent, and the dispersion is performed in an amount of 0.01 to 2.
A method of producing a foamable rubber-modified styrene resin by impregnating a foaming agent in a state where an electrolyte is present in an amount of 0 mol / l is exemplified.

The expandable rubber-modified styrene resin particles of the present invention are heated and foamed to form rubber-modified styrene resin expanded particles. As this method, for example, a method of heating to about the glass transition temperature (about 100 ° C.) of the rubber-modified styrenic resin by steam or the like can be mentioned.

Further, the obtained rubber-modified styrenic resin foam particles can be molded by using, for example, a molding machine used for producing a polystyrene foam molded article. That is, the foamed particles are filled in a mold, and the foamed particles are fused together by steam heating. After cooling for a predetermined time, the foamed particles are taken out of the mold to obtain a foamed molded article. The foamed molded article of the present invention can be molded in a short cooling time, and the obtained molded article has an expansion ratio of 50 times (molded article) and has a 2 ×
After 4 hours, it has excellent impact resistance with a 50% breaking height of 35 to 45 cm as described later in Examples, and 50 to 80 cm.
It has excellent flexibility of 1 mm, excellent appearance of molded products, and is well-balanced. Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

[0023]

【Example】

Example 1 A rubber-modified styrene-based resin shown in Table 1 was melted by a 30 mm single screw extruder, and was then made into spherical particles of about 1.4 mg / month by an underwater cutting die. 600 g of the obtained rubber-modified styrene resin particles were mixed with 900 g of ion-exchanged water, 4.0 g of sodium pyrophosphate, 8.0 g of magnesium sulfate, 0.45 g of sodium dodecyl sulfate, and 2.0 g of sodium sulfate in a 3-liter autoclave equipped with a stirrer. Put in 1
The temperature was raised to 00 ° C. over 1 hour, and after reaching 100 ° C., 23 g of pentane and 40 g of butane were added. After maintaining at 100 ° C. for 5 hours as it was, the temperature was raised to 120 ° C. over 2 hours, and after maintaining for 2 hours, cooled to 30 ° C.

The pentane used had a composition of 80% n-pentane and 20% i-pentane, and the butane used had a composition of 70% n-butane and 30% i-butane. The foamable rubber-modified styrene resin particles obtained from the autoclave were taken out, the magnesium pyrophosphate adhered to the surface was dissolved with nitric acid, washed with water, and then centrifuged. Next, the expandable rubber-modified styrene resin particles are placed in a metal cylindrical container having an inner diameter of 10 cm and a height of 25 cm on which a metal mesh having a mesh of 0.1 mm is attached at the top and bottom, and dry nitrogen at about 20 ° C. at a flow rate of 500 liters per minute Was blown from the bottom of the cylindrical container for 10 minutes and dried.

0.06 parts by weight of zinc stearate, 0.04 parts by weight of sorbitan tristearate and 100 parts by weight of bishydroxyethylalkylamine (Lion) as an antistatic agent per 100 parts by weight of the obtained expandable rubber-modified styrene resin particles. Co., Ltd., trade name Armostat 410) 0.005 parts by weight are mixed and coated, then put into a 30 liter batch type foaming machine equipped with a stirrer, and blown with steam having a pressure of 1.0 kgf / cm ² to heat and foam. Thus, foamed rubber-modified styrene resin particles of 20 kg / m ³ were obtained.

The foamed particles thus obtained were filled in a molding die, heated at a steam pressure of 0.7 kgf / cm ² for 20 seconds, cooled with water for 5 seconds, and allowed to cool to obtain a foamed molded body. Rubber particle size, butadiene content, butadiene rubber microstructure, Z-average molecular weight of rubber-modified styrene resin, internal water content, volatile foaming agent content and volatility in foamable resin particles obtained as described above Foaming agent composition, surface appearance of foamed molded product, release time during molding, compressive strength, flexural strength, 50
The% fracture height and flexibility were evaluated by the following methods.

Measurement of rubber particle size of rubber-modified styrene resin;
In a transmission electron microscope observation photograph, rubber particles 100 to
The particle diameter of 200 particles was measured and calculated by the following equation. Average particle size = ΣNiD ² / ΣNiD (where Ni is the number of rubber particles and D is the rubber particle size) Determination of butadiene content and microstructure of butadiene rubber; It was dissolved and adjusted to a concentration of 10% by weight, and tetramethylsilane was used as an internal standard (δ 0.0 ppm) to give a 67.8M
The ¹³ C-NMR spectrum was measured at Hz to determine the butadiene content and the microstructure of the butadiene rubber.

Measurement of Z-average molecular weight: A rubber-modified styrene resin is dissolved in a 0.25% by weight chloroform solution.
The insoluble matter was removed by filtration and measured using gel permeation chromatography. Measurement of internal water content: After the dried foamable rubber-modified styrene resin particles were dissolved in dry toluene, the internal water content was measured by the Karl Fischer method.

Measurement of the amount of volatile foaming agent: After the weighed sample was heated at 120 ° C. for 4 hours, it was weighed again, and the ratio of the weight of the sample before heating to the weight loss before and after heating was defined as the amount of volatile matter. Volatile blowing agent composition: 1 g of a sample was dissolved in 20 ml of dimethylformamide, and the composition ratio of the blowing agent was determined by gas chromatography.

Cooling time: The thickness of the molded product is equal to the inner size of the mold (5
0.7mm) is the time required to reach the same thickness. If the cooling time is insufficient, the thickness of the molded product will be larger than the mold size after demolding.

Surface appearance: The surface appearance of the foamed molded article was visually evaluated according to the following criteria. ；: Almost no shrinkage, melt, or gap. Δ: Shrinkage, melt, gaps are observed. X; remarkable shrinkage, melt, and gaps are observed. Compressive strength: The obtained foam is 50 mm long, 50 mm wide,
The test piece was cut to a thickness of 25 mm, and was JIS Z 02
The compressive strength (kgf / cm ² ) was measured according to No. 34.

Flexural strength: The obtained foam was 300 m long
m, 75mm in width, 25mm in thickness and cut into test pieces,
Flexural strength (kgf / c) according to JIS A 9511
m ² ) was measured. 50% breaking height; the obtained foam was 200 mm long and 4 wide.
0mm, cut into 25mm thickness to make a test piece, weight 25
5 g of a steel ball was dropped and measured according to JIS K 7211.

Flexibility: The obtained foam was 200 mm long,
Prepare a test specimen cut to a width of 30 mm and a thickness of 20 mm, and ten cylindrical shafts having different diameters of 10 mm each from 100 mmφ to 10 mmφ, and apply the center of the test specimen to the upper surface of the circumference of the cylindrical shaft. Fold from both sides along the cylinder axis in about 5 seconds. First, a test was performed using a cylindrical shaft having a shaft diameter of 100 mmφ. The same test was performed by changing the shaft diameter to a smaller one until the test piece broke, and the value of the shaft diameter when the test piece was cracked was recorded. The flexibility was evaluated from the average value (mm). Therefore, the smaller the value, the better the flexibility.

Example 2 The procedure of Example 1 was repeated, except that the composition of the rubber-modified styrene resin was changed as shown in Table 1. Table 2 shows the results. Example 3 It carried out similarly to Example 1 except having 22 g of pentane and 38 g of butanes as blowing agents, and also using 7 g of cyclohexane. Table 2 shows the results.

Example 4 The procedure of Example 1 was repeated except that the foaming agent was 54 g of butane and 7 g of cyclohexane was used. Table 2 shows the results. Example 5 It carried out similarly to Example 1 except having 72 g of butanes as a foaming agent. Table 2 shows the results.

Comparative Example 1 The procedure of Example 1 was repeated except that the blowing agent was changed to 57 g of pentane. Table 2 shows the results. Comparative Example 2 600 g of the resin particles used in Example 1 were mixed with 90 parts of ion-exchanged water.
0 g, 4.5 g of tribasic calcium phosphate, and 0.027 g of sodium dodecylbenzenesulfonate were placed in a 3 liter autoclave equipped with a stirrer. Table 2 shows the results.

Comparative Example 3 The procedure of Example 1 was repeated except that the rubber-modified styrene resin was changed as shown in Table 1. Table 2 shows the results. Comparative example 4 It carried out similarly to Example 1 except having changed into rubber modified styrene resin as shown in Table 1. Table 2 shows the results. Comparative Example 5 The same procedure was performed as in Example 1 except that the rubber-modified styrene resin was changed as shown in Table 1. Table 2 shows the results.

[0038]

[Table 1]

[0039]

[Table 2]

From the above results, it can be seen that each of the examples satisfying the constitutional requirements of the present invention gives a foam molded article excellent in appearance and strength of the molded article, and has a short cooling time during molding. In Comparative Example 1 using only pentane as the blowing agent, the cooling time was long. In Comparative Example 2 having a large internal water content, it can be seen that a part of the foamed particles on the surface of the molded product melted and collapsed, and the appearance of the molded product was deteriorated. Comparative Example 3 in which butadiene rubber particles dispersed in the resin are small and a rubber-modified styrene resin having a low Z-average molecular weight is used, and a rubber-modified styrene resin composed of a butadiene rubber having a low proportion of 1,4-cis structure It can be seen that Comparative Example 4 using was inferior in falling ball impact strength and flexibility. It can be seen that in Comparative Example 6 having a large mineral oil content, the molded product was significantly shrunk and the moldability was poor.

[0041]

By using the foamable rubber-modified styrenic resin of the present invention, it is possible to obtain a foam molded article which can be molded in a short cooling time and has excellent appearance and strength.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-25059 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 9/16, 9/228 C08L 51 / 04

Claims (5)

(57) [Claims] 1. A butadiene rubber having a ratio of 1,4-cis structure of 70% or more is contained in an amount of 8 to 15% by weight, the butadiene rubber is particulate, and the average particle diameter of the particles is 1.5%.
A rubber-modified styrene-based resin comprising a rubber component having a particle size of about 3.0 μm and a styrene-based resin, wherein the rubber component is dispersed in the styrene-based resin, and the mineral oil content in the resin is 3.0% by weight. % Or less, an internal water content of 0.2% by weight or less, and a volatile foaming agent containing butane as a main component in an amount of 1 to 15%.
Foamable rubber-modified styrenic resin particles, characterized in that the styrene-based resin particles are contained by weight. 2. The expandable rubber-modified styrenic resin particles according to claim 1, which contains cyclohexane. 3. The styrene resin has a Z-average molecular weight of 35.
The expandable rubber-modified styrenic resin particles according to claim 1, which has a molecular weight of not less than 000. 4. Expanded rubber-modified styrene resin particles obtained by heating and expanding the expandable rubber-modified styrene resin particles according to claim 1. 5. A foamed rubber-modified styrenic resin molded article comprising the foamed rubber-modified styrenic resin particles according to claim 4, having a density of 10 to 600 kg / m ³ .