JPH11263869A - Foamable styrene resin particle and molded foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain foamable styrene resin particles excellent in the balance between permeation prevention and thermoformability by coating the surfaces of foamable styrene resin particles with a specific fluorine-contg. vinyl copolymer and pullulan. SOLUTION: A fluorine-contg. vinyl copolymer is prepd. by copolymerizing 30-95 wt.% fluorine-contg. vinyl monomer of formula I (wherein Rf is Cn F2n+1 ; n is 1-16; R1 is H or a 1-18C alkyl; R2 is a 1-10C alkylene; and R3 is H or methyl) and 5-70 wt.% vinyl monomer of formula II (wherein R4 is H or methyl; and R5 is a 4-22C alkyl). 100 pts.wt. foamable styrene resin particles, 0.005-0.3 pt.wt. pref. 0.01-0.2 pt.wt. fluorine-contg. vinyl copolymer obtd. as above, and 0.001-0.1 pt.wt. pullulan having an average mol.wt. of 500-100,000 and a glass transition point of 30-100 deg.C are mixed to coat the surfaces of the particles with the fluorine-contg. vinyl copolymer and the pullulan.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable styrenic resin particles and foamed molded articles which are suitable as containers for contents in which the resulting foamed molded article contains an emulsifier component and a fat component.

[0002]

2. Description of the Related Art In general, expandable styrene resin particles are pre-expanded by steam or the like to form pre-expanded particles, and the pre-expanded particles can be filled in a mold having small holes and heated again to be molded. . The molded article thus obtained exhibits excellent properties such as economy, light weight and hygiene, and is used in many fields as a packaging material, a heat insulating material, a container and the like.

Here, the expandable styrene resin particles are formed by a blowing agent (in general, a liquid or gaseous aliphatic hydrocarbon at room temperature,
For example, propane, butane, pentane, hexane, and the like) are dispersed in an aqueous medium together with styrene resin particles, and the particles are impregnated with a foaming agent, or toluene, cyclohexane, or the like having solubility in the styrene resin particles. It is produced by a method in which a foaming agent is impregnated in an aqueous suspension containing a small amount of a solvent. Then, the expandable styrene resin particles thus obtained are molded through the above-described steps.

However, since the obtained molded article is obtained by stacking expandable styrene resin particles on a stone wall and fusing them by foaming pressure and heat, there are cases where the resin particles are not integrated. is there. As a result, when used as a container, the contents may penetrate into the outer wall of the container or the inside of the molded article depending on the type of the contents to be stored. In order to prevent such penetration, the method of minimizing the void inside the molded article, which is a way when the infiltrating contents penetrate the inside of the container, and reducing the surface energy of the particle surface In general, a method of increasing the contact angle of the surface of the molded article with respect to the infiltrating contents can be adopted.

[0005] The former method is generally carried out by strengthening the heating conditions at the time of molding. In order to obtain a molded article having less defects, the molding temperature is set lower.
A method of heating the expandable styrene resin particles for a long time has been adopted. However, this method requires a long time to heat the expandable styrene-based resin particles, and significantly reduces the productivity in the molding industry, so it is hard to say that this method is useful.

On the other hand, the latter method involves increasing the amount of a metal soap (carboxylate) generally used for preventing agglomeration of expandable styrene resin particles in prefoaming. Is being done. However, even in this method, it is necessary to lengthen the molding heating time in order to prevent the property of inhibiting fusion of the expandable styrene resin particles caused by the metal soap, and it is still difficult to say that this method is industrially useful. .

In view of the above, various expandable styrene-based resin particles have been proposed in which the content is less permeable due to a shorter molding heating time. For example, in Japanese Patent Publication No. 56-34172, expandable styrene resin particles whose surface is coated with a sucrose ester or a derivative thereof are coated with a specific perfluoroalkyl group-containing copolymer or the like in JP-A-2-88652. The expandable thermoplastic resin particle composition used as the styrene-based resin particles having a coating layer containing a metal salt of ricinoleic acid is disclosed in JP-A-2-115242, and in JP-A-3-190941. Foamable styrene resin particles coated with a copolymer of a specific fluorine-containing vinyl monomer and a lipophilic monomer are disclosed. Also, JP-A-62-158730 discloses that
Disclosed are expandable thermoplastic resin particles coated or contained with a copolymer consisting of a fluorine-containing vinyl polymer portion and a hydrophilic vinyl polymer portion.

[0008]

However, JP-B-56-34172, JP-A-2-88652, JP-A-2-115242 and JP-A-3-1.
The expandable styrenic resin particles or expandable thermoplastic resin particle composition disclosed in JP-A-90941 has excellent shielding properties (anti-penetration properties) for general aqueous (including emulsified) or oily contents. However, depending on the type of contents contained in the molded article when processed into the molded article, there is a possibility that the penetration preventing performance may be insufficient. That is, the container molded from the expandable styrene-based resin particles described above has a wide range of applications due to its economy, heat retention, etc. However, there is a possibility that the contents may permeate.

Of course, the expandable styrenic resin particles disclosed in Japanese Patent Publication No. 56-34172 and the like have some oily contents having high permeability (for example, curry roe containing a mixture of an emulsifier component and a fat component, machine Oil and the like) can exhibit excellent shielding properties (penetration prevention properties) by being subjected to heat molding for a relatively long time. However, it cannot be denied that productivity is reduced due to long-time heat molding.

The foamable thermoplastic resin particles disclosed in Japanese Patent Application Laid-Open No. 62-158730 use a copolymer comprising a fluorine-containing vinyl polymer portion and a hydrophilic vinyl polymer portion. However, there was a problem that the compatibility of the fluorine-containing vinyl monomer and the hydrophilic vinyl monomer, which are the raw materials of the copolymer, was poor, and the characteristics of the copolymer were likely to vary.

Therefore, when the expandable thermoplastic resin particles disclosed in Japanese Patent Application Laid-Open No. 62-158730 are heat-molded into a container (cup) such as an instant noodle, the emulsifier component and the fat component are contained in the distribution inventory. There is a possibility that contents such as mixed fats and oils, curry components and soup components may ooze to the outer wall of the container (cup) under the influence of temperature and humidity. In addition, when heat-molded as a returnable box for machine parts, since the returnable parts are used with the mechanical parts immersed in machine oil, the return of the returnable box may occur during repeated use of the returnable box. Sometimes penetrated into the outer wall of the building.

That is, even in the expandable styrene-based resin particles disclosed in any of the above-mentioned patent publications, the shielding property (penetration preventing property) for contents having high permeability and the productivity represented by the molding heating time are required. (Balance)
Was not always satisfactory.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. Even when the present invention is used for a container or the like in a part of highly permeable contents, the content to be accommodated is the outer wall of the container or the molded product. An object of the present invention is to provide expandable styrene-based resin particles which are less likely to penetrate into the inside and can be molded in a short time and have an excellent balance of these properties, and a foam molded article using the same.

[0014]

According to the present invention, there is provided a fluorine-containing vinyl monomer represented by the following general formula (I): 30 to 95% by weight and a vinyl-based vinyl monomer represented by the following general formula (II): Expandable styrene resin particles obtained by coating a coating containing a fluorine-containing vinyl copolymer obtained by polymerizing 5 to 70% by weight of a monomer and pullulan on the surface of the expandable styrene resin particles. About.

[0015]

Embedded image (Wherein, R _f is a fluorinated alkyl group represented by C _n F _{2n + 1} (n is an integer of _{1 to} 16), and R ₁ is hydrogen or C ₁ to C ₁
An alkyl group of 18, R ₂ represents an alkylene group having 1 to 10 carbon atoms, and R ₃ represents a hydrogen or methyl group. )

[0016]

Embedded image (In the formula, R ₄ represents hydrogen or a methyl group, and R ₅ represents 4 to 22 alkyl groups.)

In the present invention, the coating amount of the fluorine-containing vinyl copolymer is set to a value within the range of 0.005 to 0.3 parts by weight based on 100 parts by weight of the expandable styrene resin particles. Is preferred.

In the present invention, it is preferable that the coating of pullulan has a value within the range of 0.001 to 0.1 part by weight based on 100 parts by weight of the expandable styrene resin particles.

By forming the expandable styrene resin particles partially containing a hydrophilic polymer in this manner, the hydrophilic polymer pullulan serves as an adhesive, and the fluorine-containing vinyl polymer becomes It is presumed that the oil repellency can be exhibited more efficiently, but even when used in a container or the like in a highly permeable oily content while maintaining excellent shielding properties of the content. In addition, the possibility that the contents to be contained permeate into the outer wall of the container or the inside of the molded article is significantly reduced.

Here, pullulan is Aureobasidium pullulan.
lans) , and is defined as a water-soluble linear glucan having a glucopyranose residue.

In forming the expandable styrene resin particles, the coating preferably contains 5-150 parts by weight of pullulan with respect to 100 parts by weight of the fluorine-containing vinyl copolymer. From the viewpoint of excellent balance between the shielding efficiency of the content and the efficiency of productivity, the amount of pullulan used in the coating is 10 to 130 parts by weight with respect to 100 parts by weight of the fluorine-containing vinyl copolymer. The value is more preferably in the range, and most preferably 50 to 12
The value is within a range of 0 parts by weight.

By including pullulan in the coating in such a range, the penetration of a hydrophilic component or an oil component can be more efficiently prevented. Therefore, even when the expandable styrene-based resin particles are used as a container for an oily content having a high permeability or an oily content in which an emulsifier component and a fat component are mixed, the contained content is a container. Less likely to penetrate into the outer wall or inside the molded product. In addition, if the amount of such pullulan is used, at the time of preheating, there is little possibility that the expandable styrene-based resin particles aggregate and agglomerate, while at the time of molding and heating, pullulan serves as an adhesive. , And excellent fusibility.

By including pullulan in the coating in such a range, the penetration of the hydrophilic component and the oil component can be more efficiently prevented. Therefore, even when the expandable styrene-based resin particles are used as a container for an oily content having a high permeability or an oily content in which an emulsifier component and a fat component are mixed, the contained content is a container. Less likely to penetrate into the outer wall or inside the molded product. In addition, if the amount of such pullulan is used, at the time of preheating, there is little possibility that the expandable styrene-based resin particles aggregate and agglomerate, while at the time of molding and heating, pullulan serves as an adhesive. , And excellent fusibility.

[0024]

Next, embodiments of the present invention will be specifically described. 1. Expandable styrene resin particles The expandable styrene resin particles of the present invention are obtained by coating the surface of the expandable styrene resin particles with a predetermined fluorine-containing vinyl polymer. (1) Expandable styrene resin particle main body The expandable styrene resin particle main body can be prepared by impregnating a styrene resin particle with a foaming agent as described above.

(A) Styrene resin particles The styrene resin particles are not particularly limited. For example, styrene homopolymer or a component copolymerizable with a styrene monomer, for example, acrylonitrile, methyl methacrylate, butyl methacrylate or the like. One or more copolymers with methacrylates, acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate, and monomers of styrene derivatives such as α-methylstyrene, chlorostyrene, vinyltoluene, etc. Coalescence can be mentioned.

(B) Foaming agent The foaming agent is not particularly limited.
Examples thereof include liquid or gaseous compounds at room temperature, such as aliphatic hydrocarbons such as butane, pentane, and hexane, and freon-based compounds such as Freon 11 and Freon 12.

(C) Impregnation of the foaming agent The method of impregnation of the foaming agent is not particularly limited. The impregnating amount of the blowing agent is 3 to 10% by weight based on the weight of the styrene resin particles.
Is preferred.

(2) Fluorine-containing vinyl copolymer A fluorine-containing vinyl monomer represented by the following general formula (I):
What is obtained by polymerizing a vinyl monomer represented by the following general formula (II) is used. (D) Fluorine-containing vinyl monomer As the fluorine-containing vinyl monomer, a compound represented by the following general formula (I) is used.

[0029]

Embedded image (Wherein, R _f is a fluorinated alkyl group represented by C _n F _{2n + 1} (n is an integer of _{1 to} 16), and R ₁ is hydrogen or C ₁ to C ₁
An alkyl group of 18, R ₂ represents an alkylene group having 1 to 10 carbon atoms, and R ₃ represents a hydrogen or methyl group. )

Specific examples of such a fluorine-containing vinyl monomer include the following. _{C 8 F 17 SO 2 -N (} CH 3) -CH 2 CH 2 OCOCH = C
_{H 2 C 8 F 17 SO 2} -N (CH 3) -CH 2 CH 2 OCOC (C
_{H 3) = CH 2 C 8} F 17 SO 2 -N (C 2 H 5) -CH 2 CH 2 OCOCH = C
_{H 2 C 8 F 17 SO 2} -N (C 2 H 5) -CH 2 CH 2 OCOC (CH
₃ ) = CH ₂

(E) Vinyl monomer As the vinyl monomer, a compound represented by the following general formula (II) is used.

[0032]

Embedded image (In the formula, R ₄ represents hydrogen or a methyl group, and R ₅ represents 4 to 22 alkyl groups.)

Examples of such vinyl monomers include:
The following can be specifically mentioned. _{CH 2 = CH-COOC 11 H} 23 CH 2 = C (CH 3) -COOC 15 H 31 CH 2 = CH-COOC 17 H 35 CH 2 = C (CH 3) -COOC 17 H 35

(F) Polymerization ratio The polymerization ratio between the fluorine-containing vinyl monomer represented by the general formula (I) and the vinyl monomer represented by the general formula (II) is as follows. The monomer is 40 to 95% by weight and the vinyl monomer is 5 to 60% by weight. If the polymerization ratio of the fluorine-containing vinyl monomer is less than 40% by weight, it is difficult to impart sufficient water repellency and oil repellency when the molded article is obtained. This will hinder fusion.

(G) Polymerization Method The polymerization method of the fluorine-containing vinyl copolymer in the present invention is not particularly limited, and examples thereof include solution polymerization and emulsion polymerization. Examples of the polymerization initiator used in the polymerization include lauroyl peroxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, and tert-butyl peroxypivalate in solution polymerization. In the emulsion polymerization, potassium persulfate, ammonium persulfate and the like can be mentioned.

(H) Amount of Fluorinated Vinyl Copolymer Used The fluorinated vinyl copolymer coating material of the present invention is based on 100 parts by weight of expandable styrene resin particles.
The value is preferably in the range of 0.005 to 0.3 parts by weight, more preferably 0.01 to 0.2 parts by weight. If the coating amount of the fluorine-containing vinyl copolymer is less than 0.005 parts by weight, sufficient oil repellency tends not to be obtained, and if it exceeds 0.3 parts by weight, the properties of the obtained foam molded article do not improve. Tend.

(3) Pullulan (i) Types of Pullulan As the pullulan that can be used in the present invention, commercially available pullulan can be used as it is. For example, pullulan PF-20 manufactured by Hayashibara Biochemical Laboratory is used. be able to.
And, as described above, the average molecular weight is 500 to 10
It is preferred to use a pullulan in the range of 000. As described above, esterulized pullulan, etherified pullulan, or hydrogenated pullulan is preferable.

Further, although the form of pullulan is not particularly limited, it is preferable to use an aqueous solution having a concentration of 1 to 30% by weight. From the viewpoint of good workability, the viscosity of the aqueous solution of the pullulan at a concentration of 5% by weight is 1 to 100%.
A value in the range of centimeter (cp), more preferably 10
It is a value within the range of 80 centimeters (cp). Further, from the viewpoint of better fusing property between expandable styrene resin particles during heat molding, the glass transition point of pullulan is set to 30 to 1
The value is preferably in the range of 00 ° C, more preferably in the range of 40 to 80 ° C.

In order to adjust the glass transition point of pullulan, to improve the flexibility, or to improve the mixing property with the fluorine-containing vinyl monomer, glycerin, ethylene glycol and the like are used as additives. , DBP (dibutyl phthalate), DOP (dioctyl phthalate), alginamide, acrylamide, starch, CMC, methylcellulose, glyoxazole, dimethylolurea, or the like.

(J) Method of Using Pullulan Pullulan can be coated on the expandable styrene resin particles after being mixed with the fluorine-containing vinyl-based monomer. Apart from the monomer,
The foamable styrene-based resin particles may be coated alone. By coating after mixing with the fluorine-containing vinyl monomer, the expandable styrene resin particles are preferably coated in a single operation with respect to the main body of the expandable styrene resin particles. The coating treatment of the main body is preferable in that the concentration unevenness due to separation from the fluorine-containing vinyl monomer is reduced.

(4) Other Coating Agent In coating the main body of the expandable styrene resin particles, a conventionally known coating agent can be used in addition to the above-mentioned copolymer. For example, metal soaps such as zinc stearate and calcium stearate used for preventing agglomeration in primary foaming, and higher fatty acid amides such as ethylenebisamide and stearamide can be mentioned. These agglomeration inhibitors are used in the foamable styrenic resin particles 1
It is preferably used in the range of 0.05 to 0.5 part by weight based on 00 parts by weight. Among them, zinc stearate is particularly excellent in agglomeration prevention effect, and is inexpensive and economical.

In the molding step, an additive having an effect of accelerating the fusion of the expandable styrene-based resin particles can also be used. As such a substance, a conventionally known substance can be used. For example, one or two of triesters, diesters, monoesters, sucrose esters, and the like of higher fatty acids such as glyceride stearate and glyceride oleate.
More than species can be used.

Furthermore, polyhydric alcohols such as glycerin, sorbitol, polyethylene glycol, and polypropylene glycol, sorbitan esters, and ethylene glycol adducts of higher fatty acids, which are used as an antistatic agent for the primary expandable styrene resin particles. One or more nonionic surfactants can be used in combination. These antistatic agents are used in the foaming styrenic resin particle body 100.
It is preferable to use within a range of 0.005 to 0.2 parts by weight based on parts by weight.

(5) Formation of Coating The method for forming the coating of the fluorine-containing vinyl copolymer and pullulan on the surface of the expandable styrene resin particle body in the present invention is not particularly limited, and is performed by a conventionally known means. be able to. For example, using a mixer such as a ribbon blender, a V-type blender, a Henschel mixer, a Loedige mixer, etc., at room temperature, at a rotation speed of 100 to 10,000 rpm,
Under the conditions of stirring time of 10 seconds to 1 hour, the coating can be formed by mixing the expandable styrenic resin particle main body, the fluorine-containing vinyl copolymer, pullulan, each of the above-mentioned coating components, and the like. . However, the expandable styrene-based resin particles, the fluorine-containing vinyl-based copolymer, pullulan, each of the above-mentioned coating components, and the like can also be individually coated in layers.

2. Expanded molded article The expanded molded article of the present invention can be obtained by molding the above-mentioned expandable styrene resin particles. That is, by using the expandable styrene-based resin particles described above, it is possible to obtain a foamed molded article in which the foamed particles are firmly fused together with a short molding heating time and the particle interface has excellent oil repellency. Can be. Here, specific molding heating conditions are not particularly limited, but as described above, foam molding is performed using a mold or the like at a heating temperature of 90 to 150 ° C. and a heating time of 1 to 60 seconds. Is preferred.
Therefore, if the foam molded article of the present invention is manufactured as described above,
For example, highly permeable oily or fatty foods such as lard, instant lamen, curry roux, mayonnaise, margarine, etc., or machine oils are directly packaged in foamed molded products (containers). Alternatively, even when the foamed molded article is contained, it is possible to effectively prevent oils and fats from penetrating to the outside of the container from between the expandable styrene resin particles constituting the foamed molded article, and to prolong the product life of the foamed molded article. It becomes possible.

[0046]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. Example 1 (a) Preparation of Sample 5.5% by weight of pentane (iso-pentane / n
0.35 to 0.60 mm including pentane weight ratio = 30/70)
2,000 g of expandable polystyrene particles (Hybeads 5SG, manufactured by Hitachi Chemical Co., Ltd.) are placed in a Henschel mixer, and while stirring, 6 g of zinc stearate, 0.4 g of sugar ester (A-10E, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 0.4 g of glycerin, and A 20% emulsion of a fluorine-containing vinyl copolymer in which 0.4 g of pullulan (Pullulan PF-20 manufactured by Hayashibara) is dissolved, and the monomer ratio of the polymer is C ₈ F ₁₇ SO ₂ -N (CH _{3) -CH 2 CH 2 OCOCH =} CH 2 70 _{wt% CH 2 = C (CH 3} ) -COOC 17 H 35 30 % by weight in a copolymer emulsion 2.2 g (solid fluorine-containing vinyl-based copolymer component 0.4 g) were sequentially added to obtain coated expandable styrene resin particles.

This was foamed to a bulk density of 10 ml / g using a mixture of hot air and steam as a heat medium in a batch-type primary foaming apparatus to obtain primary foamed resin particles. After aging for 16 hours at normal temperature and normal pressure, the mixture was filled in a mold for obtaining a molded product having an inner volume of 500 CC and a wall thickness of 2.0 mm, and was subjected to heat molding for the heating time shown in Table 1. At this time, in addition to the heating time, 8 seconds were required for filling the raw material, cooling, and the like.

(B) Performance evaluation 1) 200 g of curry roe was added to the obtained cup to confirm the shielding property of oils and fats, and then packed with Saran wrap.
Leaching test under an atmosphere of 2 ° C. 2) As a confirmation of the shielding property of the emulsifier, an aqueous solution of a surfactant (a score roll 700 manufactured by Kao Corporation:
(0.1% by weight) and about 300 g of the compound were added to the outer wall of the cup, and the time to start the penetration was measured.

[Comparative Example 1] A cup-shaped molded product was obtained in the same manner as in Example 1 except that only the fluorinated copolymer was used and foamable styrene resin particles were used. Table 1 shows the evaluation results.

[Comparative Example 2] A cup-shaped molded product was obtained in the same manner as in Example 1 except that only the pullulan was removed and foamable styrene resin particles were used. Table 1 shows the evaluation results.

Comparative Example 3 A cup-shaped molded product was obtained in the same manner as in Example 1, except that the fluorinated copolymer and pullulan were replaced with expandable styrene resin particles. Table 1 shows the evaluation results.

[0052]

[Table 1]

[0053]

According to the present invention, when a foam molded article (cup) is molded, even if the content is highly permeable, the time required for the content to penetrate to the outer wall of the foam molded article (penetration time) is reduced. It can be made significantly longer. In particular, it has excellent shielding properties even for highly permeable contents such as curry roe, and can hold the contents for an extremely long time. Further, by configuring the expandable styrene resin particles in this manner, the productivity of the expandable styrene resin particles is not impaired while having the above excellent shielding properties. Advantageous Effects of Invention According to the present invention, it has become possible to provide expandable styrene-based resin particles and a foam molded article having an excellent balance between the shielding property of a highly permeable content and the heat moldability.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/06 C09D 133/06

Claims (4)

[Claims] 1. A fluorine-containing vinyl monomer represented by the following general formula (I): 30 to 95% by weight and a vinyl monomer represented by the following general formula (II): 5 to 70% by weight Foamable styrene resin particles obtained by coating a surface of a foamable styrene resin particle main body with a coating containing a fluorine-containing vinyl copolymer obtained by polymerizing the above, and pullulan. Embedded image (Wherein, R _f is a fluorinated alkyl group represented by C _n F _{2n + 1} (n is an integer of _{1 to} 16), and R ₁ is hydrogen or C ₁ to C ₁
An alkyl group of 18, R ₂ represents an alkylene group having 1 to 10 carbon atoms, and R ₃ represents a hydrogen or methyl group. ) (In the formula, R ₄ represents hydrogen or a methyl group, and R ₅ represents 4 to 22 alkyl groups.) 2. A coating of a fluorine-containing vinyl-based copolymer with respect to 100 parts by weight of expandable styrene-based resin particles,
2. A value within a range of 0.005 to 0.3 parts by weight.
The expandable styrene resin particles according to the above. 3. The amount of the coating of pullulan is 0.001 to 0.1 with respect to 100 parts by weight of the expandable styrene resin particles.
3. The expandable styrenic resin particles according to claim 1, wherein the value is within a range of parts by weight. 4. A foam molded article obtained by subjecting the expandable styrene resin particles according to claim 1 to foam molding.