WO2005085337A1

WO2005085337A1 - Method for producing pre-expanded particles of polyolefinic resin

Info

Publication number: WO2005085337A1
Application number: PCT/JP2005/002385
Authority: WO
Inventors: Mamoru Tsugawa; Masahide Ebisui; Yutaka Yanagihara; Takayuki Goda
Original assignee: Kaneka Corporation
Priority date: 2004-03-05
Filing date: 2005-02-09
Publication date: 2005-09-15
Also published as: JPWO2005085337A1; JP4818101B2

Abstract

A method for producing pre-expanded particles wherein polyolefinic resin particles are dispersed in an aqueous dispersant in a pressure vessel, are heated to a temperature higher than the softening temperature of the resin particles under pressure, and then are released into an atmosphere having a pressure lower than the pressure in the inside of the pressure vessel to pre-expand, characterized in that the pre-expanded resin particles are released from the releasing port of the pressure vessel in a direction different from that of the axis of the pipe for releasing and are collided with a collision plate. The above method can be advantageously employed for producing good pre-expanded polyolefinic resin particles with simplicity and ease by the use of a process wherein particles are collided with a collision plate or a wall surface of a vessel at the time of pre-expansion.

Description

Specification

Method for producing polyolefin resin pre-expanded particles

The present invention relates to a method for producing polyolefin resin pre-expanded particles. More specifically, the present invention relates to a method for producing polyolefin-based resin pre-expanded particles which can be suitably used, for example, as a raw material for in-mold foam molded articles. Background art

Conventionally, a method of manufacturing polyolefin resin pre-expanded particles by dispersing polyolefin-based resin particles in an aqueous dispersion medium in a pressure-resistant container, heating and impregnating with a volatile foaming agent, and then discharging into a low-pressure container. Is commonly done. The variation in the magnification of the pre-expanded particles is expressed by the following equation (Equation 1). Generally, the smaller the variation in the magnification, the better. If the magnification variation of the pre-expanded particles is large, it becomes difficult to obtain the pre-expanded particles of the target magnification in the production process of the pre-expanded particles, so that production control becomes difficult and the yield is deteriorated. In addition, the weight variation of the in-mold foam molded article using the pre-expanded particles as a raw material increases, and it becomes difficult to produce an in-mold foam molded article having good characteristics, resulting in an increase in defective products. . Therefore, the variation in magnification is smaller and better.

Five

2

(Equation 1) Variation in magnification xlOO

In the formula, K _av is the weight fraction of each of the particles remaining after sieving when sieved with JIS Z88 (standard sieve (8 types of 3.5, 4, 5, 6, 7, 8, 9, and 10 meshes) ^, From expansion ratio Ki. The average ratio obtained by the formula: K _av = XW.

r _m is the weight fraction Wi of each sieve residual foamed particles upon screened I divided by 828,801 standard sieve (3.5,4,5,6,7,8,9,10 eight mesh), the expansion ratio, the formula : Standard deviation obtained by m ^{= W} i ^X ( ^K a _V - ^K i) ² ¾

A method for producing polyolefin resin pre-expanded particles with reduced magnification variation has already been disclosed (for example, see Patent Documents 1 and 2). These methods are characterized in that all the pre-expanded particles released from the discharge section are made to collide with the collision plate or the container wall, but the collision plate substantially reduces the volume in the container, The colliding pre-expanded particles may accumulate in the container and be difficult to send to the subsequent process, which may cause problems in production and production.

If mass production is not performed before the pre-expanded particles can be sent smoothly, the collision particles may gradually accumulate in the container and block the interior, making production impossible. In some cases, it may be a trouble that leads to damage to the device. [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-82148

[Patent Document 2] Japanese Patent Application Laid-Open No. 2003-192820 Disclosure of the Invention

The present invention solves the above-mentioned problems of the prior art, improves the particle feedability with a simple and inexpensive apparatus, and makes it possible to industrially mass-produce polyolefin-based resin pre-expanded particles with a small variation in magnification. The task is to do it. As a result of intensive studies, the present inventors disperse the polyolefin resin particles in an aqueous dispersion medium in a pressure vessel and heat the resin to a temperature higher than the softening temperature of the resin stand. Pre-expanded particles are discharged from the discharge section of the pressure-resistant container in a direction different from the axial direction of the discharge distribution when the bubbles are released under a lower-pressure atmosphere, and collide with the collision plate. As a result, it has been found that the particle sending property of the pre-expanded particles is improved, and the present invention has been completed.

That is, in the present invention, the polyolefin-based resin particles are dispersed in an aqueous dispersion in a pressure vessel, heated to a temperature equal to or higher than the softening temperature of the resin particles, pressurized, and then subjected to a pressure lower than the internal pressure of the pressure vessel. During prefoaming by discharging, the mixture of the polyolefin resin particles and the aqueous dispersion medium in the discharge pipe is discharged from the discharge part of the pressure-resistant container in a direction different from the flowing direction and collides with the collision plate. The present invention also relates to a method for producing pre-expanded polyolefin resin particles.

In a preferred embodiment,

(1) the collision angle when the pre-expanded particles collide with the collision plate is 5 to 85 degrees, (2) the discharge portion has a plurality of apertures,

(3) When the pre-expanded particles collide with the impingement plate, the collision angle and collision distance of the pre-expanded particles released from the plurality of openings of the discharge section are substantially equal.

(4) The impact plate force is the S container wall surface,

(5) The aperture of the discharge part is a throttle plate with a cylinder,

Embodiments in which technical elements such as are added to the method for producing the pre-expanded polyolefin-based resin particles can be mentioned.

According to the present invention, when the polyolefin-based resin particles are pre-expanded, the pre-expanded particles are discharged from the discharge portion of the pressure-resistant container in a direction different from the axial direction of the discharge pipe, and are caused to collide with the collision plate. Thus, the pre-expanded particles of the polyolefin resin with small dispersion in magnification can be industrially mass-produced. Brief Description of Drawings

FIG. 1 is an illustration of a method for producing pre-expanded particles in one embodiment of the present invention. FIG. 2 is an explanatory diagram of a method for producing pre-expanded particles according to one embodiment of the present invention. FIG. 3 is an explanatory diagram illustrating an example of an axial cross section of a throttle plate with a cylinder. In the figure, 1 is a throttle plate, 2 is a low-pressure vessel, 3 is a collision plate, 4 is a pressure vessel, 5 is an aqueous dispersion medium, 6 is resin particles, 7 is a discharge pipe, and 8 is pulp. Numeral 9 indicates pre-expanded particles, 10 indicates a cylinder attached to an orifice, and 11 indicates an orifice opening. In FIGS. 1 and 2, A represents the collision angle, and D represents the collision distance. Mahiroko The arrow in Fig. 3 indicates the direction in which the expanded particles are released. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail. Hereinafter, “%” and “parts” are based on weight unless otherwise specified.

The polyolefin resin used in the present invention, the Orefin based monomer unit virtuous Mashikuho 5 0-1 0 0 Weight ^_0/0, more preferably 7 0 to: I 0 containing 0%, Orefu I It is a resin containing preferably from 0 to 50%, more preferably from 0 to 30%, of a monomer unit copolymerizable with a monomeric monomer. Since it contains 50% or more of the olefin monomer unit, a molded article that is lightweight and has excellent mechanical strength, workability, electrical insulation, water resistance, and chemical resistance can be obtained.

Specific examples of the above-mentioned olefin monomer include cyclic olefins such as α-olefin monomer having 2 to 8 carbon atoms such as ethylene, propylene, butene, pentene, hexene, heptene and octene, and norpoleneene monomer. I can fist. These may be used alone or in combination of two or more. Of these, ethylene and propylene are preferred because they are inexpensive and the properties of the resulting polymer are improved.

The monomer unit copolymerizable with the olefin monomer is a component that can be appropriately used for modifying adhesiveness, transparency, impact resistance, gas barrier property, and the like.

Specific examples of the monomer copolymerizable with the above-mentioned olefin monomer include vinyl acetate / Such as beer alcohol esters, methyl methacrylate, ethyl acrylate, hexyl acrylate, etc., alkyl (meth) acrylate esters having 1 to 6 carbon atoms, bier alcohol, methacrylic acid, vinyl chloride, etc. Can be These may be used alone or in combination of two or more. Of these, vinyl acetate is preferred from the viewpoint of adhesiveness and flexibility; low-temperature characteristics, and methyl methacrylate is preferred from the viewpoint of adhesiveness, flexibility, low-temperature characteristics, and thermal stability.

Specific examples of the polyolefin-based resin comprising the above-mentioned olefin-based monomer or copolymerizable monomer include, for example, ethylene-propylene random copolymer, ethylene-propylene-butene random terpolymer, polyethylene-polypropylene Block copolymer, polypropylene resin such as homopolypropylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer And polyethylene-based resins, such as polybutene and polypentene. These polyolefin-based dendrites may be used in a non-crosslinked state, or may be used after being crosslinked by peroxide or radiation. These polymers may be used alone or in combination of two or more. Among these,-. Polypropylene resin has less variation in magnification compared to other polyolefin resins, and it is easy to obtain pre-expanded particles with high expansion ratio, and it is manufactured from the obtained pre-expanded particles. This is preferable because the mechanical strength and heat resistance of the molded article are good.

The melt index (Ml) of the polyolefin-based resin is, for example, preferably from 0.2 g / 10 minutes to 50 g / 10 minutes for a polypropylene-based resin, more preferably 1 g / 10 minutes. More preferably, it is not more than 30 g Z l 0 min.

When the MI is less than 0.2 g / 10 minutes, the melt viscosity is too high, and it may be difficult to obtain preliminary expanded particles having a high expansion ratio. The melt viscosity with respect to the elongation of the resin is low, so that the foam tends to break, and it tends to be difficult to obtain pre-expanded particles having a high expansion ratio.

The flexural modulus (JISK 7203) is, for example, polypropylene In the case of resin-based resins, it is preferably at least 500 OMPa and not more than 200 OMPa, and more preferably at least 800 OMPa and not more than 160 OMPa. If the flexural modulus is less than 50 OMPa, the mechanical strength and heat resistance may be insufficient.If the flexural modulus exceeds 200 OMPa, the flexibility and cushioning properties of the obtained foamed molded product may be insufficient. It tends to be insufficient. For example, the melting point of the polypropylene resin is preferably from 125 ° C to 165 ° C, and more preferably from 130 ° C to 160 ° C. When the melting point is lower than 125 ° C, the heat resistance may be insufficient. When the melting point is higher than 165 ° C, the adhesiveness during molding and the secondary foaming power tend to be insufficient. In the present invention, the foaming agent is not particularly limited, and a known one such as a volatile foaming agent, an inorganic gas, and water can be used.

Specific examples of the volatile foaming agent include aliphatic hydrocarbons such as propane, i-butane, n-butane, i-pentane, n-pentane, and hexane; and fats such as cyclobutane, cyclopentane, and cyclohexane. Cyclic hydrocarbons: Examples include trichloromouth monochloromethane, dichlorodiphenololemethane, dichlorotetrafluoroethane, and trichlorotrifluoroethane, and the like. These may be used in war insects, or in combination of two or more. -.

As the inorganic gas, economy, productivity, safety, carbon dioxide from the viewpoint of environmental compatibility, nitrogen, air, or these entities (usually 5 0% by volume or more, further 7 0 volume ^_0/0 or more It is preferable to use an inorganic gas containing an inert gas such as argon, helium, xenon, or a small amount of water vapor, oxygen, hydrogen, ozone, etc. (50% by volume or less, more preferably 30% by volume or less). However, nitrogen and air are more preferable because the effect of reducing the variation in magnification is large.

When these volatile blowing agents or inorganic gases are used as the blowing agent, the blowing agent is preferably used in an amount of 2 to 50 parts, more preferably 5 to 40 parts, per 100 parts of the polyolefin-based resin particles. If the amount is less than 2 parts, the desired expansion ratio may not be obtained.If the amount is more than 50 parts, it exceeds the limit of impregnating the resin particles and the pressure rises, which is wasteful. is there.

When water is used as the blowing agent, polyolefin resin and hydrophilic polymer It is preferable to use polyolefin-based resin particles in combination.

The hydrophilic polymer is a polymer having a water absorption of 0.5% or more as measured according to ASTM D570, and is a so-called hygroscopic polymer, a water-absorbing polymer (without being dissolved in water and having its own weight. It is a concept that contains a water-soluble polymer (a polymer that dissolves in water at room temperature or high temperature) and a water-soluble polymer that absorbs water several to several hundred times that of water and is hard to dehydrate under pressure. The molecule of the hydrophilic polymer contains a hydrophilic group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, an ester group, and a polyoxyethylene group.

Examples of the hygroscopic polymer include a carboxyl group-containing polymer, a polymer, a thermoplastic polyester-based elastomer, and a cellulose derivative.

Specific examples of the above-mentioned lipoxyl group-containing polymer include, for example, a terpolymer of ethylene-acrylinoleic acid-maleic anhydride (water absorption: 0.5 to 0.7%), and a copolymer of ethylene-mono (meth) acrylic acid. Carboxylic acid groups are converted into salts with alkali metal ions such as sodium ion and potassium ion, and ionomer resins cross-linked between molecules (water absorption 0.7 to 1.4%), ethylene mono (meth) acrylic acid copolymer Coalescence (water absorption 0.5 to 0.7%). Specific examples of the polyamide include, for example, nylon-16 (water absorption: 1.3 to 1.9%), nylon-16, 6 (water absorption: 1.1 to 1.5%), copolymer Nylon (EMS—made by CHEMI E AG, trade name: grill tettas, etc.) (water absorption: 1.5 to 3%). Further, specific examples of the thermoplastic polyester-based elastomer include, for example, a block copolymer of polybutylene terephthalate and polytetramethylene glycol (water absorption: 0.5 to 0.7%). And specific examples of the cellulose derivative include, for example, cellulose acetate, cellulose propionate and the like. These may be used in insects or in combination of two or more.

Among the hygroscopic polymers, a water-containing polyolefin-based resin composition having excellent dispersibility in a polyolefin-based resin, a relatively small amount and a high water content can be obtained, and a pre-expansion having a desired expansion ratio and a small variation in magnification. Particles can be obtained, ionomer type Resins are preferred.

Examples of the water-absorbing polymer include, for example, a cross-linked polyacrylate polymer, a starch-acrylic acid graft copolymer, a cross-linked polyvinyl alcohol polymer, a cross-linked polyethylene oxide polymer, and an isobutylene-maleic acid polymer. And copolymers.

Specific examples of the cross-linked polyacrylate polymer include, for example, ί, Aqualic (trade name) manufactured by Nippon Shokubai Co., Ltd., and Diamond: (trade name) manufactured by Mitsubishi Chemical Corporation. And crosslinked poly (sodium acrylate) polymers. Specific examples of the crosslinked polybutyl alcohol polymer include various crosslinked polybutyl alcohol polymers represented by, for example, Aqua Reserve GP (trade name) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Further, as a specific example of the crosslinked poly: ^ thylene oxide-based polymer, for example, a crosslinked polyethylene oxide-based polymer represented by acork (trade name) manufactured by Sumitomo Seika Co., Ltd. may be used. . Specific examples of the isobutylene-maleic acid-based copolymer include, for example, isoptile-maleic acid-based copolymer represented by K-I gel (trade name) manufactured by Kuraray Co., Ltd. These may be used alone or in combination of two or more.

Among the water-absorbing polymers, crosslinked polyethylene oxide is a dispersant in a polyolefin-based resin and has a high water content with a relatively small amount.

Examples of the water-soluble polymer include poly (meth) acrylic acid-based polymer, poly (meth) acrylate-based polymer, polybutyl alcohol-based polymer, polyethylene oxide-based polymer, and water-soluble cell. Mouth derivatives and the like.

Specific examples of the poly (meth) acrylic acid-based polymer include, for example, polyatalylic acid, an allylic acid-ethyl acrylate copolymer, and polyhydroxy / ethyl methacrylate / hydroxyethyl. Further, specific examples of the poly (meth) acrylate polymer include ^ S and the like such as sodium polyatalylate, sodium polymethacrylate, potassium polyacrylate, and potassium potassium methacrylate. Further, specific examples of the polyvinyl alcohol-based polymer include, for example, polyvinyl alcohol. Alcohol, butyl alcohol monoacetate butyl copolymer and the like can be mentioned. Further, specific examples of the polyethylene oxide-based polymer include, for example, polyethylene oxide having a molecular weight of tens of thousands to millions. Specific examples of the water-soluble cellulose derivative include, for example, carboxymethylcellulose and hydroxyethyl cellulose. These may be used alone or in combination of two or more.

The above-mentioned hygroscopic polymer, water-absorbing polymer and water-soluble polymer may be used alone or in combination of two or more.

The amount of the hydrophilic polymer used varies depending on the type of the hydrophilic polymer, but the polyolefin-based resin particles are dispersed in an aqueous dispersion medium in a pressure vessel, and are preferably at or above the softening temperature of the polyolefin-based resin. It is preferable to obtain polyolefin-based resin particles having a water content of 1 to 50% when heated to a temperature equal to or lower than the softening temperature + 20 ° C. Usually, with respect to 100 parts of the polyolefin-based resin, Thus, the amount is preferably at least 0.05 part, more preferably at least 0.1 part. In addition, the production stability and foaming characteristics during the production of the pre-expanded particles are improved, and the molded article obtained from the pre-expanded particles is given excellent mechanical strength and heat resistance, and the dimensional change during water absorption is reduced. The amount is preferably 20 parts or less, more preferably 10 parts or less.

The polyolefin-based resin particles used in the present invention contain a filler, that is, an inorganic filler and Z or an organic filler, so that dispersion of the magnification is small, bubbles are uniform, and a relatively high foaming ratio is required. Preferred because foamed particles can be obtained V

Specific examples of the inorganic filler include talc, calcium carbonate, and hydroxide. Among these inorganic fillers, talc is preferred in that it has low expansion ratio, uniform cells, and gives pre-expanded particles having a relatively high expansion ratio.

The organic filler is not particularly limited as long as it is solid at a temperature equal to or higher than the softening temperature of the polyolefin resin. Specific examples of the organic filler include, for example, a fluororesin powder, a silicone resin powder, and a thermoplastic polyester resin powder. End.

The filler may be used in war insects, or two or more kinds may be used in combination.

The average particle diameter of the filler is such that pre-expanded particles having uniform cells and a relatively high expansion ratio can be obtained, and a molded article having excellent mechanical strength, flexibility, and the like can be obtained from the pre-expanded particles. From the viewpoint of being obtainable, it is preferably 50 μ 得る η or less, more preferably 10 μm or less, and preferably 0.5 μm or more, more preferably 0.5 m from the viewpoint of secondary aggregation and handling workability. The above is preferable.

The amount of the filler to be used is preferably at least 0.01 part with respect to 100 parts of the polyolefin-based resin, and more preferably at least 0, in order to obtain pre-expanded particles having a relatively high expansion ratio. It is preferable that the content be 0.05 parts or more. Further, when forming using the pre-expanded particles, excellent fusion properties are exerted, and the pre-expanded particles have excellent mechanical strength and flexibility. From the viewpoint of obtaining a molded product, the amount is preferably 3 parts or less, more preferably 2 parts or less.

The polyolefin-based resin particles containing the polyolefin-based resin and, if necessary, a hydrophilic polymer, a filler, and the like, are usually melt-kneaded using an extruder, a kneader, a pan-pally mixer, a roll, or the like, and then have a columnar or oval shape. It is preferably obtained by molding into a desired resin particle shape which is utilized for foaming, such as columnar, spherical, cubic, or rectangular parallelepiped. The conditions for producing the resin particles, the size of the resin particles, and the like are not particularly limited.For example, resin particles obtained by melt-kneading in an extruder are usually 0.5 to 5 mg / particle. It is.

The resin particles as described above are dispersed in an aqueous dispersion medium containing a dispersant and a dispersing agent in a pressure vessel, and the resin particles are heated to a temperature equal to or higher than the softening temperature of the polyolefin resin, and the foaming agent is converted into resin particles. Impregnate.

The aqueous dispersion medium in which the resin particles are dispersed may be any solvent that does not dissolve the polyolefin resin. Normally, water or water and one or more of ethylene glycol, glycerin, methanol, ethanol, and the like, or two or more thereof are used. Mixtures with more than one species are exemplified, but water is preferred from the environmental and economical aspects.

Specific examples of the dispersant include, for example, tricalcium phosphate, basic magnesium carbonate Examples include inorganic salts such as nesium, basic zinc carbonate and calcium carbonate, and clays such as bentonite and potassium phosphate. Of these, tricalcium phosphate is preferred because of its strong dispersing power.

Examples of the dispersing aid include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium n-paraffin sulfonate, sodium α-olefin sulfonate, and sodium alkylnaphthalene sulfonate; And other cationic surfactants. Among these, sodium η-paraffin sulfonate is preferred because it gives a good dispersing power and is easily produced.

The amount of the polyolefin-based resin particles dispersed in the aqueous dispersion medium is preferably from 3 to 100 parts of the polyolefin-based resin particles to 100 parts of the aqueous dispersion medium, and more preferably from ΓΟ to 5 parts. 0 parts or less are preferable. If the amount of the polyolefin-based resin particles is less than 3 parts, the productivity may be reduced and the economy may not be economical.If the amount is more than 100 parts, there is a possibility that the resin particles tend to fuse together in the container during the heat of calo. There is.

The amount of the dispersing agent and the dispersing agent is not particularly limited, and any commonly used amount may be used. However, the dispersing agent is used in an amount of 0.0 with respect to 100 parts of the polyolefin resin particles. The content is preferably 5 parts or more and 10 parts or less, and the dispersing aid is preferably 0.005 parts or more and 1 part or less with respect to 100 parts of the polyolefin resin particles! /.

In the present invention, the polyolefin-based resin particles are dispersed in an aqueous dispersion medium, and then heated and pressurized to a temperature equal to or higher than the softening point of the polyolefin-based resin. After dispersing the polyolefin-based resin particles in an aqueous dispersion medium in a pressure vessel, the polyolefin-based resin particles should be expanded to a temperature and pressure at which they can be expanded by adjusting the quality of the pre-expanded particles such as the magnification and the variation in the magnification. Since there is no influence, either heating or pressurization may be performed first.

The temperature at which the polyolefin-based resin particles are dispersed and heated is a temperature equal to or higher than the softening temperature of the polyolefin-based resin to be used, specifically, equal to or higher than the melting point, preferably equal to or higher than the melting point + 5 ° C. + 20 ° C or less, more preferably

Melting point + 15 ° C or less. For example, when using an ethylene-propylene copolymer having a melting point of 145 ° C, the lower limit is 145 ° C, preferably 150 ° C. The The upper limit is preferably 165 ° C, more preferably 165 ° C.

If the temperature is lower than 144 ° C, foaming becomes difficult.If the temperature exceeds 165 ° C, the mechanical strength and heat resistance of the obtained pre-expanded particles are not sufficient, and the resin particles are fused and chewed in the container. May be.

As the gas for pressurizing the inside of the pressure vessel, the volatile foaming agent and / or the inorganic gas described above can be used. The holding pressure in the pressure vessel is 0.6 ~

7.5 MPa is preferred, and 1.0 to 3.0 OMPa is more preferred.

If the holding pressure is less than 0.6 MPa, the polyolefin-based resin particles may not foam, and pre-expanded particles having a desired expansion ratio may not be obtained. On the other hand, if the pressure exceeds 7.5 MPa, the bubbles of the pre-expanded particles obtained become too small, and the closed cell rate tends to decrease, resulting in a tendency for molded articles to shrink, to lose shape stability, mechanical strength, and heat resistance. is there.

When the foaming agent is water, the resin particles are dispersed in an aqueous dispersion medium, heated, and stirred, for example, for 30 minutes to 12 hours, so that the water content of the resin particles is 1 to 50%. After that, an inorganic gas is introduced into the pressure-resistant container to set the pressure of the pressure-resistant container to 0.6 to 7.5 MPa, and while maintaining this pressure, in an atmosphere having a pressure lower than the internal pressure of the pressure-resistant container. The polyolefin-based resin pre-expanded particles are produced by causing the water-containing resin particles to be discharged after passing through a squeezing machine with a tube.

The adjustment of the water content can be performed by adjusting the heating temperature, the heating time, and the like. When the water content is less than 1%, the kishi foam ratio tends to be less than twice. The preferred moisture content is 2% or more. If the content exceeds 50%, the dispersibility of the polyolefin-based resin particles in the aqueous dispersion medium is reduced, and the polyolefin-based resin particles become lump in the pressure vessel during the production of the pre-expanded particles, and cannot be uniformly foamed. Cheap. The preferred water content is 30% or less. Since the water absorption of the hydrophilic polymer is a value measured at room temperature, and the water content is a value measured at a high temperature (resin melting point), for example, the water absorption of the used hydrophilic polymer is 0.5% or more. If so, a water content of 1% or more can be obtained.

In the present invention, the polyolefin-based resin particles may be mixed with a polyolefin-based resin. Or more, so that the water content is usually 1 to 50%, and the foaming ratio is preferably about 2 to 43 times, more preferably about 3 to 15 times, and the prefoaming is low in magnification variation. Particles can be obtained. Further, in the present invention, the polyolefin-based resin particles do not clump in the pressure-resistant container during the production of the pre-expanded particles, and uniform pre-expanded particles can be obtained.

The softening temperature of the polyolefin-based resin is determined from the temperature at the top of the melting peak when measured by a DSC (differential scanning calorimeter) at a heating rate of 10 ° CZ.

The water content is the water content under the water vapor pressure at the temperature or higher, and is obtained as follows.

That is, in a 300 cc pressure-resistant ampoule, 50 g of resin particles comprising the polyolefin resin composition, 150 g of water, 0.5 g of powdery basic calcium phosphate tribasic as a dispersing agent, and dispersion were conducted. After adding 0.33 g of sodium n-paraffin sulfonate as an auxiliary agent, after sealing, heat treatment is performed for 3 hours in an oil bath set at a temperature not lower than the softening temperature of the polyolefin resin. After cooling to room temperature, the resin was taken out, washed thoroughly with water to remove the dispersing agent, and the weight (X) of the obtained water-containing resin particles of the polyolefin resin composition obtained by removing the water adhering to the surface was obtained. After drying in an oven set at a temperature 20 ° C higher than the melting point of the polyolefin resin particles for 3 hours, the weight (Y) after cooling to room temperature in a desiccator is determined, and the following equation (Equation 2) is obtained. It is required accordingly. The water content in the case where a filler or the like is contained in the resin particles of the polyolefin resin is a water content based on the total amount of the polyolefin resin and the hydrophilic polymer.

(Equation 2) Moisture content (%) = ^ 1 _ ^ _{χ 100}

After reaching the specified pressure by pressurizing with gas, the polyolefin resin particles are There is no particular limitation on the time required for release into the low-pressure atmosphere together with the dispersion medium, but it is preferable that the time be as short as possible from the viewpoint of improving productivity. In addition, it is preferable that the pressure in the container during the discharge be maintained at the ultimate pressure.

The pressure lower than the internal pressure in the pressure-resistant container may be lower than the internal pressure in the pressure-resistant container, and may be a pressure. Usually, a pressure near the atmospheric pressure is selected. The atmosphere refers to a space containing the scattered trajectory of the discharged aqueous dispersion (pre-expanded particles and aqueous dispersion medium), but is generally a pipe or duct-shaped device that is shielded from the outside air. Go inside.

The production of the polyolefin-based resin pre-expanded particles is carried out by discharging a mixture of the polyolefin-based resin particles and the aqueous dispersion medium in an atmosphere having a pressure lower than the internal pressure of the pressure vessel. During the release of the mixture, it is desirable to introduce an inorganic gas or the like into the pressure-resistant container to maintain the internal pressure of the pressure-resistant container in order to obtain pre-expanded particles having a certain magnification.

A discharge pipe having pulp is usually arranged between the pressure vessel and the discharge section. In the present invention, the discharge section of the pressure vessel is used to discharge the mixture of the polyolefin-based resin particles and the aqueous dispersion medium. The mixture is discharged in a direction different from the flowing direction of the mixture in the discharge pipe. Due to the structure of the equipment, the discharge pipe may not be straight (L-shaped, etc.). In such a case, it refers to the direction in which the mixture of the polyolefin resin particles and the aqueous dispersion medium closest to the discharge section flows. By controlling the collision angle at the discharge section in this manner, the degree of freedom in the position and angle of the collision plate is increased, and the particle feedability is improved. When industrial mass production is to be carried out continuously or semi-continuously, it is preferable that the released pre-expanded particles be immediately transferred to the subsequent process.For example, a method of mechanically sending the pre-expanded particles in a scraping manner, Combined with the method of flushing with water or air, the particle feedability is further improved.

In general, it is preferable to use a squeezing disk in the discharge section for adjusting the release time and making the expansion ratio uniform. Among them, the use of an orifice plate is preferable because the flow rate can be kept constant, high-magnification, pre-bubble particles with little variation in magnification can be obtained, and the structure is simple. The orifice plate is an orifice type , Nozzle type, bench lily type, etc., and these may be combined.

When using an orifice plate, the orifice diameter (ha) should be between 0.5 and

6. Omm, more preferably 1.0 to 4.0 Omm. When the diameter is less than 0.5 mm, the opening is easily closed by the resin, and when the diameter exceeds 6. Omm, the variation in magnification of the obtained pre-expanded foam particles deteriorates.

Further, the thickness (b) of the orifice plate is preferably 0.2 to 10 mm, more preferably 0.5 to 5 mm. If the thickness is less than 0.2 mm, the orifice plate is likely to be damaged by the pressure at the time of discharge.If the thickness exceeds 10 mm, the expansion ratio of the obtained pre-expanded foam particles is reduced, and the desired expansion ratio is obtained. It becomes difficult to obtain pre-expanded particles, and the resin may block the openings.

In this effort, it is preferable to provide a plurality of openings in the discharge section. Since the production speed increases with the number of holes, mass production can be performed efficiently. The upper limit of the number of apertures is not particularly limited, but in the case of an industrial process, it is preferable to appropriately adjust the processing capacity so as not to exceed the processing capacity of a post-process.

The collision plate referred to in the present invention is a device provided at a position where the water-containing particles discharged from the discharge section collide. The size of the impingement plate may be a size capable of causing the pre-expanded particles to collide, and the shape may be a flat plate or a convex plate or a concave plate in the scattering direction of the pre-expanded particles. It is preferable to use a pipe or duct-shaped container wall as a collision plate installed at a position surrounding the plurality of discharge portions because the device is simpler. Of course, when adjusting the collision distance or collision angle, the collision plate may be installed when the container wall is used as the collision plate.

In order to produce the pre-expanded particles having a small magnification variation, the lower limit of the distance (D) from the discharge section to the collision plate is preferably 5 mm, more preferably 1 Omm. The upper limit is preferably 1500 mm, more preferably 1000 mm, and particularly preferably 80 Omm. If the distance is less than 5 mm, the distance between the discharge portion and the impact plate is too small, and the pre-expanded particles tend to fuse together at the discharge portion and hardly foam. Also, depending on the heating and pressurizing conditions in the pressure vessel, magnification variation may occur if the distance is more than 150 Omm. The luster reduction effect may be reduced. If the distance to the impingement plate is too long, the pre-expanded particles cool down before the collision and become difficult to expand, and the magnification is lost.At the same time, the unevenness in cooling between the pre-expanded particles before the collision causes a large variation in magnification. Because there is, it is preferable to decide according to the comfort bubble conditions.

The material of the impact plate is not particularly limited, but may be metal, plastic, rubber, felt, ceramics, or wood.

Usually, at the time of prefoaming, when the temperature falls below the softening temperature of the polyolefin-based resin particles, the resin hardens and foaming ends. When the mixture of the polyolefin resin particles and the aqueous dispersion medium collides with the collision plate as in the present invention, it is considered that the temperature and humidity of the foaming atmosphere become more uniform. Foams uniformly, and the variation in magnification is reduced.

The collision angle in the present invention refers to the angle of incidence when the pre-expanded particles collide with the collision plate, 90 degrees when colliding from directly in front, and 0 degrees when scattered in parallel with the collision plate and does not collide. Then, it can take a value between 0 degrees and 90 degrees or less. The collision angle may be any angle at which the pre-expanded particles can collide, and is not particularly limited. From the viewpoint that pre-expanded particles having a more uniform cell diameter can be obtained, the collision angle is preferably 5 degrees or more. More preferably, it is 0 degree or more. In addition, it is preferably at most 85 degrees, more preferably at most 45 degrees, from the viewpoint that the pre-expanded particles after the collision are more easily sent. In the present invention, the collision angle can be adjusted by both the discharge part and the collision plate.

In the case where the discharge portion has a plurality of openings, in order to obtain pre-expanded particles having a small variation in magnification, which is the object of the present invention, the pre-expanded particles released from the plurality of openings are each the same. It is desirable to hit the impact plate. In other words, it is desirable to install apertures and impact plates so that the collision angle and collision distance of the pre-expanded particles released from the multiple apertures are equal! /.

For this purpose, for example, it is preferable to provide openings in the radial direction so that the direction of release of the pre-expanded particles is radial as viewed from the axial direction of the discharge pipe. In addition, the collision plate is installed at a position surrounding the discharge part so as to correspond to each opening. 2385

17 is preferred.

When using an orifice plate for the discharge part, it is possible to arrange a plurality of flat orifice plates side by side in order to provide openings in the radial direction. It is preferable to provide a plurality of openings in the orifice plate because they can be simplified and downsized. For example, an orifice plate with an opening on the side of a cylindrical or polygonal column, an orifice plate with an opening on the side of a cone or polygon, or a spherical or hemispherical surface with an opening on the side. An orifice plate having an opening may be used. In order to achieve this easily, for example, as shown in FIG. 1 or FIG. 2, the low-pressure vessel has a shape that is axisymmetric about the central axis, for example, a cylindrical shape or a polygonal column, and is installed around the discharge part, What is necessary is just to make the discharge | emission part each become an equal angle from a center axis. Alternatively, the collision plate may be installed for the discharge section in any direction, though the device becomes complicated.

When releasing the pre-expanded particles from the discharge section, it is desirable to install a throttle plate with a tube in the discharge section and discharge through this. This is because the pre-expanded particles released by passing through the cylinder are less likely to spread, and the individual particles collide at a more uniform collision distance and collision angle.

The shape of the cylindrical body of the throttle plate with a cylinder will be described with reference to FIG. The diameter of the cylinder is the inner diameter. It is preferable that the cylinder is integrally attached to the discharge side of the orifice plate. The material of the cylindrical body is not particularly limited, but generally, a metal is used and is integrally formed with the orifice plate. The method of integration is welding, fitting, screwing, It does not matter whether it is bonded or not, and in some cases, it can be made as the same product.

The opening area on the opposite side where the cylinder is attached to the orifice plate cannot be specified unconditionally depending on the size and length of the cylinder, but in general, it is sufficient if it is at least 1.3 times the opening area of the orifice. is there. If the ratio is 1.3 times or less, the pre-expanded particles to be released tend to agglomerate or clog. If the length of the cylinder is short, the above problem does not occur, but the effect of the cylinder is less likely to occur.

The shape of the cylindrical body may be a prism or a column. In this case, the shape of the opening of the cylindrical body is a square. The width or minor axis (H a) of the front is 0.6 mm or more, preferably 1.2 to 25 mm, and the tube length (L) is 5 mm or more, preferably 5 to It has a shape of 30 O mm. If the width or minor axis (H a) of the front of the slit or circle of the cylindrical body is less than 0.6 mm, the slit or hole is likely to be closed. When the cylinder length (L) is less than 5 mm, the scattering trajectory of the released aqueous dispersion is not different from the case of using a diaphragm with no cylinder, and there is no effect of reducing the variation in magnification. If the length is longer than O mm, the pre-expanded particles may collide with each other and fuse in the cylinder, so that the pre-expanded particles may not be obtained.

Further, the shape of the cylindrical body may be a part of a pyramid or a conical shape.The area of the portion in contact with the orifice plate is close to the opening area of the orifice, but after passing through the cylindrical body the The opening area of the cylinder at the time when the dispersion is released is large.

The slit shape in the present invention means a through hole having a polygonal shape such as a rectangle, a square, a rhombus, a trapezoid, a parallelogram, another square, a triangle, a pentagon, and a hexagon, and the circular hole is a circle. A through hole having a shape such as an elliptical shape, a rectangular shape, or a shape in which a semicircle having a diameter on the opposite side is added to two opposite sides of a rectangle or square. The width or major axis of the rectangle is the height or minor axis, respectively, the long side and the minor side (the same is true for a square), and the trapezoid is the larger of the base or height is the smaller of the width or major axis. In the height or minor axis, in other cases, the longest line segment of the straight line passing through the center of gravity of the opening shape and cut by the side is the major axis, and the shortest is the minor axis. In the case of an ellipse, the major axis and minor axis are the width or major axis height or minor axis, respectively.In other cases, a straight line passing through the center of gravity of the opening shape is a line segment cut by a side. The longest one is the S major axis, and the shortest one is the minor axis.

When two or more cylinders of the throttle plate with a cylinder are provided, each cylinder has a slit shape or a circular shape, and may have the same shape or may have different shapes. However, the present invention can be carried out, for example, as follows. If necessary, polyolefin-based resin particles containing a hydrophilic polymer and a filler are dispersed in an aqueous dispersion medium containing a dispersant and a dispersing aid in a pressure-resistant container, and the polyolefin resin particles are converted into a polyolefin-based resin. Heat to a temperature equal to or higher than the temperature to impregnate the resin particles with the foaming agent. After dispersing the polyolefin resin particles in an aqueous dispersion medium, the dispersion is heated to a temperature higher than the softening point of the polyolefin resin, preferably

Pressurize the pressure vessel until the pressure reaches 0.6 to 7.5 MPa. Pressurization may be performed first and then heating may be performed. The water content of the polyolefin resin particles is preferably adjusted to 1 to 50% by adjusting the heating and pressurizing temperatures. The polyolefin resin particles having the desired water content as described above are discharged, for example, under a low-pressure atmosphere at atmospheric pressure, which is constituted by a pipe or duct-like device that is isolated from the outside air.

At this time, in the present invention, it is preferable that the mixture is discharged from the discharge portion of the pressure-resistant container in a direction different from the direction in which the mixture flows in the discharge pipe, and the mixture is made to collide with a container wall such as a pipe or a duct. Further, it is preferable from the viewpoint of productivity that the discharge section has a plurality of openings.

The pre-expanded particles from the polyolefin-based resin particles thus obtained preferably have an expansion ratio of about 2 to 43 times, more preferably about 3 15 times. When the expansion ratio is less than about 2 times, it may not be enough to obtain a molded article requiring flexibility, cushioning properties, and the like. Strength and heat resistance may be insufficient. Further, the closed cell rate is preferably 80 to 100%, more preferably 90 to 100 ° / ₀ , and the average cell diameter is preferably 10 to 500 μηι, More preferably, it has a size of 50 to 300 μm. If the closed cell ratio is less than 80%, the secondary foaming power may be insufficient, and poor fusion may occur at the time of molding, and the mechanical strength of the obtained molded article may be reduced. The polyolefin resin foam particles having a closed cell ratio of 80% or more can be air-impregnated by subjecting the pre-expanded foam particles to heating and pressurization in a pressure vessel for a certain period of time, if necessary, for molding. It is possible to produce a molded product according to the mold by filling in the mold and subjecting it to foam heating by steam heating. Further, if the average cell diameter is less than 10 μm, there is a possibility that a problem such as distortion of the shape of the obtained molded article may occur, If it exceeds 500 μηι, the mechanical strength of the obtained molded article may decrease. The foamed molded article thus obtained has excellent flexibility and cushioning properties, and has a small dimensional shrinkage and small shape deformation, so that it has extremely high commercial value. 〔Example〕

Next, the ability to explain the production method of the present invention based on examples will not be limited to only these examples.

(Example 1)

Ethylene-propylene random copolymer, a polyolefin resin (density 0.91 gZcm ³ , ethylene content 3%, melting point 145 ° C, Ml = 5.5 g / 10 min, flexural modulus; OO OMP a) 100 parts by weight of a hydrophilic polymer (an ionomer obtained by neutralizing the carboxyl group of an ethylene-methacrylic acid copolymer with sodium ions (consisting of 85% ethylene units and 15% methacrylic acid units, 60% of methacrylic acid units) Is a salt, MI -0.9 g 10 min, melting point 89 ° C, water absorption 1%)) 2 parts Talc (average particle size 7 μπι) 0.3 parts as inorganic filler Is added and fed to a 50 mm φ single screw extruder.

Extruded from a 1.5 mm mm cylindrical die, water-cooled and cut with a cutter to obtain resin particles (pellets) (1.8 mg / particle) from a cylindrical polyolefin resin composition. (Water content measured at an oil bath temperature of 154.5 ° C by the above-mentioned water content measurement method was 5.0%, and the water content was 5.0%) 100 parts (500 kg), 0.5 parts of tribasic calcium phosphate as a dispersant and dispersion After charging 0.01 part of n-paraffin sodium sulfonate as an auxiliary agent together with 300 parts of water into the pressure-resistant container 4 of the apparatus shown in FIG. 1, while stirring the aqueous dispersion in the container to 155.0 ° C. Heated. The pressure inside the pressure vessel at this time was about 0.5 MPa. After that, the internal pressure of the pressure vessel is adjusted to 0.8 to 3. OMPa by air pressure so that the expansion ratio becomes 10 times, and the valve 8 at the lower part of the pressure vessel is immediately opened to mix the resin particles and the aqueous dispersion medium. Was released from the discharge section 1 to obtain pre-expanded particles having a closed cell structure. Pressure in pressure vessel during discharge The pressure was maintained with air so that the pressure did not decrease.

At this time, the orifice plate of the discharge part has an orifice port with a diameter (ha) of 3.0 mm on the side surface of a circular pipe with an outer diameter of 30 mm and a thickness (b) of 5 mm at an equal interval of 72 degrees. We used orifice plates that were installed at five locations. A metal cylindrical duct container with an inner diameter of 63 mm is installed at the discharge section, and an orifice is set at the center of the duct, parallel to the flow direction of the mixture of polyolefin resin particles and the aqueous dispersion medium in the discharge pipe. It was installed as follows. At this time, as shown in Table 1, the collision distance (D) was 300 mm, and the discharge angle (the flow direction of the mixture of the polyolefin resin particles and the aqueous dispersion medium in the discharge pipe and the discharge direction of the pre-expanded particles) Angle) is 90 degrees, and the collision angle (A) is 90 degrees. (Device shown in Fig. 1)

The released pre-expanded particles were sent to the post-process by a blower, and all the charged resin was released to obtain pre-expanded particles. The magnification variation was as good as 6%.

(Expansion ratio) Pre-expanded particles weigh about 3 to 10 g, dry at 60 ° C for 6 hours or more, measure weight w, measure volume V by 7 dip method, specific gravity

seeking p _b = wZv, the ratio between the density P _r of the material composition was determined expansion ratio K = P _r Zi) _b.

table 1

(Example 2)

The orifice plate of the discharge part is located at an angle of 70 degrees from the central axis. The thickness (b) is 5 mm. An orifice plate with an inner diameter (Ha) of 7.0 mm and a length of 30 mm (L) was used. At the discharge section, a metal cylindrical duct container with an inner diameter of 235 mm was installed around the orifice so as to be parallel to the flow direction of the mixture of polyolefin resin particles and aqueous dispersion medium in the discharge pipe. . At this time, as shown in Table 1, the collision distance (D) is 300 mm, the emission angle is 20 degrees, and the collision angle (A) is 20 degrees. Otherwise in the same manner as in Example 1, pre-expanded particles were obtained. The released pre-expanded particles were reflected by the collision plate and scattered to the back of the duct container, and while being smoothly sent to the subsequent process, all the charged resin was released and pre-expanded particles could be obtained. . The magnification variation was as good as 4%.

(Example 3)

The orifice plate of the discharge part is located on the side of a conical plate with a thickness (b) of 5 mm and an angle of 70 degrees with the central axis. The diameter (ha) of the orifice is 3. Omm. Five orifice plates provided at equal intervals of 72 degrees were used. The low-pressure vessel uses a metal cylindrical duct vessel with an inner diameter of 235 mm, and the orifice is installed at the center of the low-pressure vessel so as to be parallel to the flow direction of the mixture of the polyolefin resin particles and the aqueous dispersion medium in the discharge pipe. did. At this time, as shown in Table 1, the collision distance (D) is 300 mm, the emission angle is 20 degrees, and the collision angle (A) is 20 degrees. Otherwise in the same manner as in Example 1, pre-expanded particles were obtained.

The released pre-foamed particles are reflected by the collision plate and scatter to the back of the duct container, and are smoothly sent to the post-process, whereupon all the charged resin is released to obtain pre-foamed particles. Was. The magnification was 6%, which was good.

(Example 4)

The orifice plate of the discharge part is composed of five orifices with a cylinder inner diameter (Ha) of 7. Omm and a cylinder length (L) of 30 mm attached to each orifice opening of the orifice plate of Example 3. Using a board (Figure 3). At this time, as shown in Table 1, the collision distance

(D) is 300 mm, the release angle is 20 degrees, and the collision angle (A) is 20 degrees. Otherwise in the same manner as in Example 3, pre-expanded particles were obtained. (The device shown in Fig. 2)

The released pre-foamed particles are reflected by the collision plate and scatter to the back of the duct container, and are smoothly sent to the post-process, whereupon all the charged resin is released to obtain pre-foamed particles. Was. The magnification variation was 4%, which was even better than in Example 3.

(Example 5)

Ethylene-propylene random copolymer, a polyolefin resin (density 0.91 g / c, ethylene content 3%, melting point 145.C, MI = 5.5 gZlO content, flexural modulus 100 OMP a) To 100 parts, 0.1 part of talc (average particle size 7.111) was added as an inorganic filler, and the mixture was fed to a 5 Omm φ single screw extruder. After feeding, melt-kneading, extruding through a cylindrical die with a diameter of 1.5 mm φ, cooling with water and cutting with a cutter, resin particles (pellets) from columnar polyolefin resin composition (1.8 mg Z particles) Got.

100 parts (3000 kg) of the obtained resin particles (water content measured at an oil bath temperature of 154.5 ° C by the above-described method of measuring water content at 154.5 ° C), 100 parts (3000 kg), and 1% calcium tertiary phosphate as a dispersant After charging 5 parts and 0.03 part of sodium n-paraffin sulfonate as a dispersing aid together with 300 parts of water in the pressure vessel 4 of the apparatus shown in FIG. 2, while stirring the aqueous dispersion in the vessel, butane was added. 12 parts were press-fitted and heated to 140 ° C. At this time, the pressure in the pressure vessel was about 1.3 MPa. After that, the pulp 8 is opened while the pressure in the pressure-resistant container 4 is maintained with butane so that the expansion ratio becomes 15 times, and the mixture of the resin particles and the aqueous dispersion medium is released from the discharge portion 1 to have a closed cell structure. Pre-expanded particles were obtained.

At this time, the discharge part had the same structure as that of Example 4 (FIG. 3). At this time, as shown in Table 1, the collision distance (D) is 300 mm, the emission angle is 20 degrees, and the collision angle (A) is 20 degrees. Otherwise in the same manner as in Example 4, pre-expanded particles were obtained. (The device shown in Fig. 2)

The released pre-expanded particles are reflected by the collision plate and scatter to the back of the T duct container, and are smoothly sent to the subsequent process, whereupon all of the charged resin can be released to obtain pre-expanded particles. Was. The magnification variation was as good as 7%.

(Example 6)

• Polyolefin-based ethylene-propylene random copolymer (density

0.91 gZcm ³ , ethylene content 3%, melting point 142 ° C, Ml = 7. Og / 10 min) Potassium ion crosslinking of ethylene- (meth) acrylic acid copolymer as hydrophilic polymer to 100 parts 2 parts of ethylene ionomer resin (trade name: Himilan SD100, manufactured by DuPont Mitsui Polychemicals), 0.2 part of melamine (trade name: Melamine BASF Ne-ring), and talc as an inorganic filler (average particle size: 7 μπι) 0.3 parts were added, and resin particles (pellets) (1.8 mg Z particles) were obtained in the same manner as in Example 1.

Pre-expanded particles were obtained in the same manner as in Example 4, except that the heating temperature of the pressure-resistant container 4 was set to 152.0 ° C. and the expansion ratio was set to 8 times.

Table 2 shows the results. The released pre-expanded particles were reflected by the collision plate and scattered to the back of the duct container, and were smoothly sent to the subsequent process, and all of the charged resin was released to obtain pre-expanded particles. . The magnification variation was as good as 7%. Table 2

(Example 7)

Example 6 except that 0.5 parts of melamine (trade name: Melamine, manufactured by BASF) was added. W

Resin particles (pellets) (1.8 mg / particle) were obtained in the same manner as in Example 26. Pre-expanded particles were obtained in the same manner as in Example 4, except that the heating temperature of the pressure-resistant container 4 was set to 152.0 ° C. and the expansion ratio was set to 24 times.

Table 2 shows the results. The released pre-expanded particles were reflected by the collision plate and scattered to the back of the duct container, and were smoothly sent to the subsequent process, and all of the charged resin was released to obtain pre-expanded particles. . The magnification variation was as good as 1%.

(Example 8)

The discharge angle of the orifice plate was 25 degrees, the collision angle (A) was 25 degrees, and the collision distance (D) was 243 mm. Otherwise in the same manner as in Example 5, pre-expanded particles were obtained. (The device shown in Fig. 2)

Table 2 shows the results. The released pre-expanded particles were reflected by the collision plate and scattered to the back of the duct container, and were smoothly sent to the subsequent process, and all the charged resin was released to obtain pre-expanded particles. . The magnification variation was good at 3%. (Example 9)

The discharge angle of the orifice plate was 15 degrees, the collision angle (A) was 15 degrees, and the collision distance (D) was 3996 mm. Otherwise in the same manner as in Example 5, pre-expanded particles were obtained. (The device shown in Fig. 2)

Table 2 shows the results. The released pre-expanded particles were reflected by the collision plate and scattered to the back of the duct container, and were smoothly sent to the subsequent process, and all of the charged resin was released to obtain pre-expanded particles. . The magnification variation was as good as 6%. (Comparative Example 1) '

The orifice plate of the discharge part is provided with 5 orifices at a distance of φ30 mm from the center of the orifice with a diameter (ha) of 3.0 mm on a flat plate with a thickness (b) of 5 mm. Used orifice plate. At the discharge part, a metal cylindrical duct container with an inner diameter of 635 mm is installed, and in front of the orifice, it is perpendicular to the flow direction of the mixture of the polyolefin resin particles and the aqueous dispersion medium in the discharge pipe. A flat collision plate was installed as follows. At this time, as shown in Table 1, the collision distance (D) is 300 mm, the discharge angle is 0 degree, and the collision angle (A) is 90 degrees. Otherwise, the pre-expanded particles were prepared in the same manner as in Example 1. Obtained.

The pre-expanded particles released at this time had a good magnification variation of 6%, but could not be sent to the subsequent process because they were blocked by the impingement plate even with the use of a blower. Production was suspended.

(Comparative Example 2)

The orifice plate of Comparative Example 1 was used as the orifice plate at the discharge part. No collision plate was installed. Otherwise in the same manner as in Comparative Example 1, pre-expanded particles were obtained.

The released pre-expanded particles were scattered to the back of the duct container without collision, and while being smoothly sent to the subsequent process, all the charged resin was released to obtain pre-expanded particles. The magnification variation was 15%, which was not as good as in Examples 1 to 4.

(Comparative Example 3)

The orifice plate of Comparative Example 1 was used as the orifice plate at the discharge part. No collision plate was installed. Otherwise in the same manner as in Example 5, pre-expanded particles were obtained.

The released pre-expanded particles were scattered to the back of the duct container without collision, and while being smoothly sent to the subsequent process, all the charged resin was released to obtain pre-expanded particles. The magnification variation was 22%, which was not as good as in Example 5.

Claims

The scope of the claims

1. Polyolefin-based resin particles are dispersed in an aqueous dispersion medium in a pressure-resistant container, heated to a temperature higher than the softening temperature of the resin particles, pressurized, and then released in an atmosphere having a pressure lower than the internal pressure in the pressure-resistant container. During prefoaming, the mixture is discharged from the discharge part of the pressure-resistant container in a direction different from the flow direction of the mixture of the polyolefin-based resin particles and the aqueous dispersion medium in the discharge pipe, and collides with the collision plate. A method for producing pre-expanded polyolefin resin particles.

2. The method for producing pre-expanded polyolefin resin particles according to claim 1, wherein the collision angle at which the pre-expanded particles collide with the collision plate is 5 to 85 degrees.

3. The method for producing polyolefin resin pre-expanded particles according to claim 1, wherein the discharge section has a plurality of openings.

4. When the pre-expanded particles collide with the impingement plate, the collision angle and collision distance of the pre-expanded particles released from the plurality of openings of the discharge section are substantially equal. 4. The method for producing pre-expanded polyolefin resin particles according to any one of claim 3.

5. The method for producing polyolefin resin pre-expanded particles according to any one of claims 1 to 4, wherein the collision plate is a container wall surface.

6. The method for producing pre-expanded polyolefin resin particles according to any one of claims 1 to 5, wherein the opening of the discharge portion is a throttle plate with a cylinder.