JPH0812798A - Polyolefin resin prefoamed particle with antistatic property and its manufacture - Google Patents

Abstract

PURPOSE:To obtain polyolefin resin prefoamed particles that give foamed products having excellent surface properties and antistatic properties and good expandability and fusibility by mixing a specific antistatic agent with a polyolefin resin. CONSTITUTION:The polyolefin resin prefoamed particles are made of a polyolefin resin composition prepared by mixing 100 pts.wt. polyolefin resin and 0.05 to 5 pts.wt. hydroxyalkylmonoethanolamine represented by the formula wherein R is an 8-22 C alkyl group. preferably, the particles of the polyolefin resin composition further contains 0.005 to 0.1 pt.wt. organic pigment per 100 pts.wt. polyolefin resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pre-expanded polyolefin resin particles having antistatic properties and a method for producing the same. More specifically, beads have good foaming properties and fusion properties,
TECHNICAL FIELD The present invention relates to a polyolefin resin pre-expanded particle which has good surface properties and antistatic properties and can provide an in-mold expanded molded article that does not cause yellowing, and a method for producing the same.

[0002]

2. Description of the Related Art In-mold foam molded articles of polyolefin resin pre-expanded particles are used as cushioning packaging materials for electronic equipment parts such as office automation equipment and general equipment parts. It is not suitable for use as a packaging material for electronic device parts that are easy to handle and are averse to dust and static electricity. For this reason,
In-mold foam moldings made of pre-expanded polyolefin resin particles having antistatic properties have begun to be developed.

As a general method for imparting antistatic property, a method of applying a hydrophilic surfactant on the surface of a molded article,
A typical method is to produce a molded product from a resin in which a surfactant is kneaded in advance.

As an example of the pre-expanded polyolefin resin particles having an antistatic property, which is used in the production of a molded product from the above-described resin in which a surfactant is kneaded, nonionic nonionic resins of HLB 4 to 8 are used. Particles from a composition containing a system surfactant are impregnated with a foaming agent, held under high temperature and high pressure, and then released under low pressure,
It has been proposed to use polyolefin resin pre-expanded particles (Japanese Patent Laid-Open No. 3-28239).

As examples of the above nonionic surfactant, N, N-di (2-hydroxyethyl) alkylamine (hereinafter referred to as alkyldiethanolamine), fatty acid monoglyceride, sorbitan fatty acid ester, and alkyldiethanolamide are suitable. It is stated that there is.

[0006]

However, when the above-mentioned antistatic agent is used, a molded article having good antistatic property is not always obtained, and the antistatic property varies depending on the antistatic agent used. It is the actual situation that there is. The antistatic property of the foamed product in the polyolefin resin mold is best when the alkyldiethanolamine is used as the antistatic agent. However, in general, when alkyldiethanolamine is used as an antistatic agent for polyolefin resins containing phenolic antioxidants, the resulting molded articles tend to turn yellow during curing / drying or during long-term storage. In the case of an inner foamed product, the slits that introduce steam turn yellow and have a mottled pattern. In the United States, it is a standard (MIL-B
-81705), there is a problem that when the resin particles are colored by containing an organic pigment or the like, color unevenness occurs on the surface of the molded product, and the commercial value is apt to be significantly reduced. In addition, if the concentration of the organic pigment in the polyolefin resin is increased to solve the problem of color unevenness, the average bubble diameter of the pre-expanded particles becomes finer, which causes a problem that the surface property of the molded product deteriorates.

[0007]

SUMMARY OF THE INVENTION In view of such circumstances, the present inventors have a tendency to prevent yellowing and have good antistatic properties.
As a result of intensive studies to obtain an excellent polyolefin-based resin in-mold molded article, it was found that the above-mentioned problems can be solved by blending a specific antistatic agent with the polyolefin-based resin. Furthermore, it has been found that even when containing an organic pigment or dye that can be generally used for coloring, by mixing a specific amount of the organic pigment, the surface property is good and color unevenness due to yellowing does not occur, The present invention has been completed.

That is, the present invention is based on the general formula (1):

[0009]

Embedded image

(Wherein R is an alkyl group having 8 to 22 carbon atoms), an antistatic property formed from particles of a polyolefin resin composition containing 0.05 to 5 parts of a hydroxyalkyl monoethanolamine is shown. Pre-expanded polyolefin resin particles, polyolefin resin 100
In addition to 0.05 to 5 parts of the hydroxyalkyl monoethanolamine represented by the general formula (1), 0.005 to 0.1 part of an organic pigment is further added to the polyolefin resin composition particles. Based on 100 parts of the formed polyolefin resin pre-expanded particles having antistatic properties and the polyolefin resin, the general formula (1):

[0011]

[Chemical 4]

Particles of a polyolefin resin composition containing 0.05 to 5 parts of a hydroxyalkyl monoethanolamine represented by the formula (wherein R is an alkyl group having 8 to 22 carbon atoms) are treated with water in a pressure resistant container. , A dispersant and a volatile foaming agent to prepare an aqueous dispersion, and the melting point of the particles-
Antistatic property, characterized in that the resin particles are impregnated with a volatile foaming agent at a temperature in the range of 20 ° C. to + 20 ° C., and the aqueous dispersion is released under pressure to a lower pressure atmosphere than in the container. In addition to 0.05 to 5 parts of the hydroxyalkyl monoethanolamine represented by the above general formula (1), an organic pigment of 0.1 part is added to 100 parts of the polyolefin resin pre-expanded particles having the above formula.
The present invention relates to a method for producing pre-expanded polyolefin resin particles having antistatic properties, which comprises using particles from a polyolefin resin composition containing 005 to 0.1 part.

[0013]

EXAMPLES The polyolefin resin referred to in the present invention contains 50% or more of olefin units and preferably has an MI of 0.1.
It is a resin of 1 to 50 g / 10 minutes.

Specific examples of the polyolefin resin include high density polyethylene (HDPE), medium density polyethylene (MDPE) and low density polyethylene (LD).
PE), linear low density polyethylene (LLDPE), polyethylene such as low molecular weight polyethylene, polypropylene, polypropylene such as low molecular weight polypropylene, other polyolefin homopolymers such as polybutene, ethylene-propylene random copolymer, ethylene -Ethylene-based copolymers such as propylene block copolymer, ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl chloride copolymer, ethylene-vinyl acetate-vinyl alcohol copolymer, propylene-1-butene Examples thereof include, but are not limited to, copolymers, propylene-based copolymers such as propylene-ethylene-butene random terpolymer, and those obtained by crosslinking these as necessary. Of these, linear low-density polyethylene (LLDPE), ethylene-propylene random copolymer, and ethylene-propylene-butene terpolymer are preferable in terms of bead foamability and in-mold moldability.

These may be used alone or in combination of two or more.

In the present invention, the above-mentioned polyolefin-based resin has the general formula (1) as an antistatic agent:

[0017]

Embedded image

A hydroxyalkyl monoethanolamine represented by the formula (wherein R is an alkyl group having 8 to 22 carbon atoms) is added.

The hydroxyalkyl monoethanolamine represented by the general formula (1) improves the antistatic property of the obtained in-mold foamed molded product, and also maintains the moldability and discoloration resistance of the molded product.

The carbon number of R in the general formula (1) is 8 to 2.
If it is 2, but less than 8 or more than 22, the antistatic effect becomes insufficient, which is not preferable.

Specific examples of R in the general formula (1) include, for example, an octyl group, a nonyl group, a pentadecyl group,
Preferred examples include linear alkyl groups such as a hexadecyl group, a heptadecyl group, and an octadecyl group, but the present invention is not limited thereto.

Polyolefin resin 10 in the present invention
The addition amount of the hydroxyalkyl monoethanolamine (antistatic agent) represented by the general formula (1) to 0 part is 0.05 to 5 parts, preferably 0.1 to 3 parts. When the amount of the antistatic agent added is less than 0.05 part, a sufficient antistatic effect cannot be obtained, while when it exceeds 5 parts, the resulting molded article tends to be sticky.

The antistatic agent is combined with another antistatic agent (for example, a nonionic surfactant such as glycerin fatty acid ester, alkyldiethanolamide, sorbitan fatty acid ester or the like, a cationic surfactant or an antistatic agent such as an amphoteric surfactant). It can be used together.

When used in combination, it is preferable that the hydroxyalkyl monoethanolamine represented by the general formula (1) is contained in an amount of 50% or more from the viewpoints of antistatic property and discoloration resistance.

The order of mixing the polyolefin resin and the antistatic agent, the manner of mixing, etc. are not particularly limited, but from a part of the polyolefin resin and the hydroxyalkyl monoethanolamine represented by the general formula (1), First,
A method of preparing a masterbatch having a high content rate of the antistatic agent, for example, a masterbatch having a content rate of the antistatic agent of 5 to 20% and mixing the masterbatch with the residual polyolefin resin is to uniformly disperse the antistatic agent. It is preferable because it is easy.

An organic pigment may be added to the polyolefin resin composition comprising the polyolefin resin used in the present invention and the hydroxyalkyl monoethanolamine represented by the general formula (1).

As the organic pigment, for example, a perylene-based or polyazo-based organic pigment is used, but the organic pigment is not limited thereto.

The content of the organic pigment is preferably 0.005 to 0.1 part with respect to 100 parts of the polyolefin resin from the viewpoint of dispersibility and antistatic property. The content is 0.
If it exceeds 1 part, the bubble diameter of the pre-expanded particles tends to be fine, and the surface properties of the molded product tend to be poor, resulting in a poor appearance.

The order of mixing the polyolefin resin and the organic pigment and the manner of mixing are not particularly limited, but as in the case of the polyolefin resin and the antistatic agent, first, a masterbatch having a high pigment content, for example, It is preferable to prepare a masterbatch having a pigment content of 0.1 to 5% and mix it with a residual polyolefin resin because the pigment can be easily dispersed uniformly.

The pre-expanded polyolefin resin particles of the present invention are pre-expanded particles having antistatic properties obtained by pre-expanding particles from the composition comprising the polyolefin resin and the antistatic agent as described above, and further The pre-expanded particles having antistatic properties are obtained by pre-expanding particles obtained by adding a specific amount of an organic pigment to the composition.

The size of the particles is generally 0.5 to 10 m.
g / grain, and the pre-expanded particles of the present invention contain such particles in an amount of usually 5 to 60 times, preferably 10 to
It is pre-foamed to about 40.

The density of the pre-expanded particles is usually 0.18 to 0.015 g / cc, more preferably 0.
It is about 09 to 0.022 g / cc.

The particles and the masterbatch are prepared by melt-kneading a polyolefin resin, an antistatic agent, an organic pigment (including the case where it is added as a masterbatch) in an extruder, and then through a plurality of openings. It is produced by extruding into a strand shape, cooling in air or water, and then cutting and granulating the strand. When using a masterbatch, the masterbatch may be used instead of the antistatic agent, the organic pigment and the like.

Next, a method of producing the polyolefin resin pre-expanded particles of the present invention will be described.

Particles of a polyolefin resin composition containing an antistatic agent and an organic pigment as described above and a volatile foaming agent are dispersed in water in the presence of a dispersant, and the melting point of the particles is from -20 ° C. Pre-expanded particles of the present invention by heating to a temperature in the range of + 20 ° C. to impregnate the particles with a volatile foaming agent and releasing the aqueous dispersion under pressure under an atmosphere at a pressure lower than that in the container. Is manufactured. When the water dispersion is discharged under a lower pressure atmosphere than the inside of the container, the temperature and pressure inside the container are kept constant, whereby pre-expanded particles having a small variation in expansion ratio can be obtained.

The volatile foaming agent has a boiling point of -50.
Hydrocarbons or halogenated hydrocarbons at up to + 120 ° C., for example, hydrocarbons such as propane, butane, pentane, hexane, heptane, cyclohexane, monochloromethane, dichloromethane, monochloroethane, trichloromonofluoromethane, dichlorodifluoroethane, dichloro Halogenated hydrocarbons such as difluoromethane, dichloromonofluoroethane, trichlorotrifluoroethane and dichlorotetrafluoroethane are used. These may be used alone or in combination of two or more.

The amount of these volatile foaming agents used is determined with respect to the resin in the particles in consideration of the type of the foaming agent, the desired expansion ratio, the ratio of the amount of particles in the container to the space volume in the container. 5
Preferably ~ 40% impregnation.

As the dispersant, an inorganic substance which is generally used as a dispersant, such as tricalcium phosphate, magnesium pyrophosphate, zinc carbonate or the like, which is poorly soluble in water, is used. Further, a small amount of anionic surfactant, which is generally used as a dispersion aid, such as sodium dodecylbenzene sulfonate or sodium α-olefin sulfonate may be used together as a dispersion aid.

The amount of the dispersant used is also a commonly used amount, and is about 0.1 to 5 parts with respect to 100 parts of the polyolefin resin. The amount of the dispersion aid used is generally 0.001 to 0.3 parts per 100 parts of the polyolefin resin, but is not particularly limited to this range. .

Further, the ratio of particles before pre-foaming in the water dispersion is not particularly limited as long as it is 20 to 100 parts with respect to 100 parts of water which is a generally adopted ratio.

From the melting point of the particles, -20 ° C to + 20 ° C
The temperature range is DSC2 manufactured by Seiko Instruments Inc.
20 is the temperature based on the melting point measured under the condition that the temperature rising rate is 10 ° C./min. -20 to +2 from melting point
The volatile blowing agent is impregnated by heating to a temperature in the range 0 ° C, preferably -10 ° C to + 10 ° C.

When the temperature is lower than (melting point -20 ° C), it becomes difficult to obtain the pre-expanded particles having a target magnification, and when the temperature is higher than (melting point + 20 ° C),
The melt viscosity of the resin is lowered too much, and the closed cell ratio of the pre-expanded particles is lowered.

The atmosphere under a pressure lower than that in the container is not particularly limited as long as it is a condition under which a low-pressure atmosphere for releasing the water dispersion in the container is generally used when producing the pre-expanded particles. For example, when it is released into the air, it is under the atmosphere, and when it is released into the closed system to recover the volatile foaming agent, it is under the atmosphere of the closed system.

The pre-expanded particles of the present invention are manufactured as described above.

Further, the obtained pre-expanded particles have moldability,
The meltability is good, and a good molded product can be obtained by ordinary in-mold foam molding.

The pre-expanded particles obtained as described above are filled in a molding die after the blowing agent in the expanded particles is replaced with air, and then internal pressure is applied as necessary or without applying internal pressure as it is. 0.7-4.0 kg / cm ²
The particles are fused with water vapor of about (G), taken out from the mold, and then aged in a drying chamber at 60 ° C. to 80 ° C. for about 24 hours to obtain a molded product.

Further, the obtained molded product is used for various purposes, but since a specific antistatic agent is used, the discoloration resistance and antistatic property of the molded product are excellent at a high level.

Hereinafter, the present invention will be described in more detail based on examples.

Examples 1 to 3 and Comparative Examples 1 to 4 Phenolic antioxidant (octadecyl-3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate) containing 0.15 parts density 0.93 g / c
m ^3, were mixed with MI2.0g / 10 min linear low density polyethylene (DSC melting point 124 ° C.) 100 parts, the type shown in Table 1, the antistatic agent and the organic pigment in an amount, 50 mm [phi]
After kneading (210 ° C.) with an extruder of No. 1 and granulating, particles (4.5 mg / grain) before pre-expansion were produced.

In a 10-liter pressure vessel, 300 parts of water, 100 parts of the obtained particles, a third dispersant and a third dispersion aid were used.
2.0 parts of calcium phosphate and 0.03 part of normal paraffin sodium sulfonate were charged, 15 parts of isobutane was further charged, and the contents were kept for 30 minutes at the temperature and internal pressure shown in Table 1 under stirring. Then, the inside of the container was filled with nitrogen gas. While maintaining the internal pressure, the aqueous dispersion was discharged under atmospheric pressure through a 5 mmφ orifice provided in the lower part of the container to obtain pre-expanded particles. After that, it was washed with water and dried.

The expansion ratio of the obtained pre-expanded particles

[0052]

[Equation 1]

Calculated from Table 1 shows the results.

Next, 450 m of the obtained pre-expanded particles are added.
It is filled in a mold of m × 300 mm × 50 mm, and the pre-expanded particles are heated with 0.8 kg / cm ² (G) of steam,
After fusion, an in-mold molded product was obtained and taken out from the mold. After the molded product taken out of the mold is dried and cured in an oven at 80 ° C for 24 hours, the physical properties of the molded product (foaming ratio of molded product,
The surface properties, fusion properties, discoloration resistance, and surface resistivity) were evaluated by the following methods. The results are shown in Table 1.

(Expansion Ratio of Molded Product) The weight of the molded product and the volume of the molded product are obtained.

[0056]

[Equation 2]

Obtained from

(Surface property) The surface of the molded product was visually observed and evaluated according to the following criteria.

◯: There are few irregularities between the surface particles and the surface is smooth. Δ: There are a large number of irregularities between the surface particles and the surface smoothness is slightly poor. X: There are many irregularities between the surface particles and the surface smoothness is poor. (Fusability) The molded product was broken and the cross section was observed and evaluated according to the following criteria.

◯: Particle breakage ratio is 60% or more ×: Particle breakage ratio is less than 60% (Discoloration resistance) The colored state of the surface of the molded product is visually observed and evaluated according to the following criteria. did.

◯: No yellowing was observed ×: Significant yellowing (surface resistivity) The molded product was stored in a room at a temperature of 23 ° C. and a humidity of 50% for 48 hours, and after adjusting the condition, Advantest Co., Ltd. It was measured using a super insulation resistance meter TR8601 manufactured by and manufactured according to the following criteria.

[0062] ○: 1 × 10 of less than ^{11 Ω △: 1 × 10 11} Ω or more ~1 × 10 of less than ^{12 Ω ×: 1 × 10 12} Ω or more

[0063]

[Table 1]

Examples 4 to 6 and Comparative Examples 5 to 8 Ethylene-propylene random copolymer (DSC melting point 145 ° C.) containing 0.2 part of phenolic antioxidant (BHT) and having an ethylene content of 3.2%. 50 parts of the antistatic agent and organic pigment of the type and amount shown in Table 2 are mixed,
After kneading (220 ° C) with an mmφ extruder, granulate,
Particles (1.8 mg / grain) before pre-expansion were produced.

In a 10 liter pressure vessel, 300 parts of water, 100 parts of the obtained particles, a third as a dispersant and a dispersion aid.
After charging 2.0 parts of calcium phosphate and 0.03 part of sodium norman paraffin sulfonate, 11 parts of isobutane were further charged, and the contents were kept for 30 minutes at the temperature and internal pressure shown in Table 2 under stirring. While maintaining the internal pressure, the water dispersion was discharged under atmospheric pressure through a 5 mmφ orifice provided at the bottom of the container to obtain pre-expanded particles. After that, it was washed with water and dried.

The expansion ratio of the obtained pre-expanded particles was determined in the same manner as in Example 1. Table 2 shows the results.

Next, the obtained pre-expanded particles were charged into a 200 liter pressure resistant container, pressurized to 8 kg / cm ² (G), and held for 2 hours to set the internal pressure of the pre-expanded particles to 1 kg / cm.
450 mm x 300 mm x 50 m after raising to ² (G)
3 m / cm of the expanded particles filled in the m mold
² (G) was heated and fused with water vapor to obtain an in-mold molded product, which was taken out of the mold. The molded product taken out from the mold was dried and cured in a dryer at 70 ° C. for 24 hours, and the physical properties of the molded product were measured in the same manner as in Example 1. Table 2 shows the results
Shown in

[0068]

[Table 2]

[0069]

EFFECTS OF THE INVENTION When a molded product is produced using the pre-expanded particles of the present invention, it is easy to obtain a molded product having good discoloration resistance and antistatic property, little stickiness, and good fusion between particles. You can get it.

Claims (4)

[Claims] 1. A compound represented by the general formula (1): embedded image with respect to 100 parts by weight of a polyolefin resin. (In the formula, R is an alkyl group having 8 to 22 carbon atoms), and a hydroxyalkyl monoethanolamine of 0.05 to
Pre-expanded polyolefin resin particles having antistatic properties, which are formed from 5 parts by weight of particles of the polyolefin resin composition. 2. The polyolefin resin pre-expanded particles according to claim 1, wherein particles of the polyolefin resin composition further containing 0.005 to 0.1 part by weight of an organic pigment are used with respect to 100 parts by weight of the polyolefin resin. . 3. A compound represented by the general formula (1): embedded image with respect to 100 parts by weight of the polyolefin resin. (In the formula, R is an alkyl group having 8 to 22 carbon atoms), and a hydroxyalkyl monoethanolamine of 0.05 to
Particles of a polyolefin resin composition containing 5 parts by weight were charged into a pressure resistant container together with water, a dispersant and a volatile foaming agent to form an aqueous dispersion, and the melting point of the particles was from -20 ° C to + 20 ° C. A polyolefin resin pre-expanded particle having antistatic properties, characterized in that the particle is impregnated with a volatile foaming agent at a temperature, and the aqueous dispersion is released under pressure under an atmosphere at a pressure lower than that in a container. Manufacturing method. 4. The method according to claim 3, wherein particles of a polyolefin resin composition further containing 0.005 to 0.1 parts by weight of an organic pigment are used with respect to 100 parts by weight of the polyolefin resin.