JP5400323B2 - Method for producing polyolefin resin pre-expanded particles with reduced amount of adhesion dispersant - Google Patents

Description

  The present invention relates to a method for producing polyolefin resin pre-expanded particles that can be suitably used for the production of a polyolefin resin foam molded article used for buffer packaging materials, boxes, heat insulating materials, automobile bumper core materials, and the like.

  Polyolefin-based resin foam moldings are widely used for automobile parts such as buffer packaging materials and bumper core materials. These polyolefin resin foam moldings are produced from polyolefin resin pre-expanded particles.

  Usually, polyolefin resin pre-expanded particles are produced by impregnating resin particles dispersed in an aqueous medium together with an inorganic dispersant in a pressure-resistant container such as an autoclave and then impregnating the resin particles impregnated with the foaming agent with resin. A method of releasing and foaming in a low-pressure atmosphere from inside the container at a temperature equal to or higher than the particle softening temperature is employed.

  At this time, in order to stabilize the dispersion state of the resin particles in the aqueous medium, the surface of the resin particles is coated to make the resin particles easy to conform to water, and has an action of preventing adhesion between the particles, aluminum oxide, Dispersants such as inorganic substance dispersants such as titanium oxide, tricalcium phosphate and kaolin, and aqueous polymer protective colloids such as N-polyvinylpyrrolidone and polyvinyl alcohol are used.

  However, these dispersants remain on the surface of the obtained pre-foamed particles, and particularly in the case of inorganic dispersants, the amount of the dispersant remains on the surface of the pre-foamed particles because the amount of use is large. There is a tendency. Such pre-expanded particles may be difficult to fuse even if the pre-expanded particles are heated in the molding process of the in-mold foam molded product, and the dispersant adhering to the pre-expanded particles is removed. It was hoped to do.

  As a method for removing the dispersant on the surface of the pre-foamed particles, a method of washing by submerging the foamed particles (Patent Document 1), a method of cleaning the sprayed particles by spraying a specific mineral acid aqueous solution (Patent Document 2), etc. It has been known. However, these methods have a problem in that a large amount of water or an acid aqueous solution is required for cleaning, and a cleaning cost and a processing cost of cleaning waste liquid are required.

Patent Document 3 is a document aimed at solving problems such as deterioration in physical properties such as deterioration in appearance and rigidity at the time of in-mold foam molding using polypropylene-based resin pre-expanded particles having a low expansion ratio. In the literature, as a dispersion aid, in addition to surfactants, strong acids such as sulfuric acid, hydrochloric acid and nitric acid, and strong acid salts such as aluminum sulfate, magnesium chloride and calcium sulfate or strong acid salt hydrates can be used. Has been. Further, it is disclosed that the amount of adhering dispersant can be reduced by using a silicate mineral as an anti-fusing agent and a strong acid salt or a strong acid salt hydrate and an anionic surfactant as a dispersion aid. However, in this patent document, the method of reducing the anti-fusing agent when tricalcium phosphate is used as the anti-fusing agent, specifically, only washing with water is disclosed in the examples. Absent.
Japanese Patent Laid-Open No. 9-124832 JP-A-8-225675 JP 2000-63556 A

  An object of the present invention is to provide a method for producing polyolefin resin pre-expanded particles in which the amount of dispersant adhering to the surface of the pre-expanded particles is reduced.

  As a result of intensive studies to solve the above problems, the inventors of the present invention placed a dispersion containing polyolefin resin particles in water, a dispersant, and a dispersion aid in a pressure vessel, and heated the contents. Thereafter, when the polyolefin resin pre-expanded particles are produced by releasing the contents under a pressure lower than that in the pressure vessel under pressure with a foaming agent, a pH adjuster is used. By adjusting the pH within a predetermined range, polyolefin resin pre-expanded particles can be produced with stable dispersion of the polyolefin resin particles in the pressure-resistant container, and there are few dispersants remaining on the surface of the pre-expanded particles. As a result, the present invention has been completed.

  That is, according to the first aspect of the present invention, a dispersion liquid containing a polyolefin-based resin particle, water, a dispersant, a dispersion aid and a foaming agent are placed in a pressure-resistant container, and the inside of the pressure-resistant container is subjected to a predetermined pressure under pressure. In a method for obtaining polyolefin-based resin pre-expanded particles by heating to a temperature and releasing the dispersion in a low-pressure atmosphere from the pressure-resistant vessel while keeping the temperature and pressure constant, using calcium phosphate as a dispersant, The present invention relates to a method for producing polyolefin resin pre-expanded particles, wherein the pH of a dispersion in a container is adjusted to 3 or more and less than 7 with a pH adjuster.

As a preferred embodiment,
(1) Adjust the pH of the dispersion in the pressure vessel to 3 or more and 6 or less with a pH adjuster;
(2) The pH adjuster is an acid and / or a weak acid salt,
(3) As the foaming agent, one or more selected from aliphatic hydrocarbons having a boiling point of 70 ° C. or less and water are used.
(4) The amount of the dispersant adhering to the polyolefin resin pre-expanded particles is 700 ppm or less with respect to the polyolefin resin pre-expanded particles.
The present invention relates to a method for producing the polyolefin resin pre-expanded particles described above.

2nd of this invention is related with the manufacturing method of the polyolefin resin foaming molding obtained by filling the polyolefin resin pre-expanded particle obtained by the said manufacturing method in a metal mold | die, and heating.

  According to the production method of the present invention, the dispersion state is stable without increasing the amount of the dispersant, and the obtained polyolefin resin pre-expanded particles have a small amount of the dispersant adhering to the surface thereof. When the pre-expanded particles are molded, a polyolefin resin foam molded article having good fusion can be obtained.

  The present invention includes a polyolefin resin particle, water, a dispersant, a dispersion liquid containing a dispersion aid and a foaming agent placed in a pressure vessel, and the pressure vessel is heated to a predetermined temperature under pressure. In the method of obtaining the polyolefin resin pre-expanded particles by discharging the dispersion under a lower pressure atmosphere than in the pressure vessel while maintaining the constant, using tribasic calcium phosphate as a dispersant, the dispersion in the pressure vessel This is a method for producing polyolefin resin pre-expanded particles, wherein the pH is adjusted to 3 or more and less than 7 with a pH adjuster.

  As the polyolefin resin constituting the polyolefin resin particles used in the present invention, high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ethylene-vinyl acetate copolymer and other polyethylene resins, propylene homopolymer, Ethylene-propylene random copolymer, ethylene-propylene block copolymer, propylene-butene random copolymer, ethylene-propylene-butene random copolymer, maleic anhydride-propylene random copolymer, maleic anhydride-propylene block Examples thereof include polypropylene resins such as copolymers, propylene-maleic anhydride graft copolymers, and styrene-modified polyolefins. These polyolefin-based resins are preferably non-crosslinked, but crosslinked resins can also be used.

  The polyolefin resin is formed into the shape of polyolefin resin particles using a known method. For example, it is melted using an extruder, a kneader, a Banbury mixer (trademark), a roll or the like, and processed into polyolefin resin particles having a weight of 0.2 to 10 mg, preferably 0.5 to 6 mg. Generally, it is preferable to melt by using an extruder and to manufacture by a strand cut method. For example, polyolefin resin particles having a desired shape can be obtained by cutting a polyolefin resin extruded in a strand form from a circular die and cooled and solidified with water, air, or the like.

  In addition, as a method for producing resin particles of styrene-modified polyolefin, for example, polyolefin resin particles are produced in the same manner as described above, and while the polyolefin resin particles are dispersed in a dispersion medium, a vinyl monomer such as styrene is used. There is a method of forming resin particles by impregnating and polymerizing the body.

  Moreover, it is preferable to add a cell nucleating agent during the production of the polyolefin resin particles because the cell diameter when the polyolefin resin pre-expanded particles can be adjusted to a desired value. As the cell nucleating agent, inorganic nucleating agents such as talc, calcium carbonate, silica, kaolin, titanium oxide, bentonite and barium sulfate are generally used. The amount of the cell nucleating agent added varies depending on the type of polyolefin resin to be used and the type of cell nucleating agent, and cannot be specified unconditionally, but is generally 0.001 part by weight or more with respect to 100 parts by weight of the polyolefin resin. It is preferable that it is below the weight part.

  Furthermore, when manufacturing the polyolefin resin particles, various additives can be added as necessary within the range not impairing the properties of the polyolefin resin. Examples of additives include colorants such as carbon black and organic pigments;

Antistatic agents such as alkyldiethanolamides, alkyldiethanolamines, hydroxyalkylethanolamines, polyether-polyolefin resin block copolymers, fatty acid monoglycerides, fatty acid diglycerides;

IRGANOX (registered trademark) 1010 (Ciba Specialty Chemicals), IRGANOX (registered trademark) 1076 (Ciba Specialty Chemicals), IRGANOX (registered trademark) 1330 (Ciba Specialty Chemicals), IRGANOX (registered trademark) 1425 WL (Ciba Specialty Chemicals), IRGANOX ( Hindered phenolic antioxidants such as (registered trademark) 3114 (registered trademark) (Ciba Specialty Chemicals);

Phosphorus processing stabilizers such as IRGAFOS (registered trademark) 168 (Ciba Specialty Chemicals), IRGAFOS (registered trademark) P-EPQ (Ciba Specialty Chemicals), IRGAFOS 126;
Lactone processing stabilizers;
Metal deactivators such as hydroxylamine-based processing stabilizers, IRGANOX® MD 1024 (Ciba Specialty Chemicals);

Benzotriazole ultraviolet absorbers such as TINUVIN (registered trademark) 326 (Ciba Specialty Chemicals), TINUVIN (registered trademark) 327;
Benzoate light stabilizers such as TINUVIN® 120;
Hindered amine light stabilizers such as CHIMASSORB 119 (Ciba Specialty Chemicals), CHIMASSORB (registered trademark) 944 (Ciba Specialty Chemicals), TINUVIN (registered trademark) 622 (Ciba Specialty Chemicals), TINUVIN (registered trademark) 770;

Flame retardant aids such as halogen flame retardants and antimony trioxide;
Non-halogen flame retardants such as FLAMESTAB (registered trademark) NOR116 (Ciba Specialty Chemicals), MELAPUR (registered trademark) MC25 (Ciba Specialty Chemicals);

Acid neutralizers such as hydrotalcite and calcium stearate;
Crystal nucleating agents such as IRGASTAB (registered trademark) NA11 (Ciba Specialty Chemicals);
Examples include amide type additives such as erucic acid amide and ethylene bis stearic acid amide.

  When these additives are used, some of them generally have a tendency to increase the amount of the adhering dispersant. In such a case, the effect of the present invention is particularly exerted. In particular, the effect of reducing the adhesion dispersant when the amide-based additive is used as the additive is remarkable.

  In the polyolefin resin pre-expanded particles in the present invention, a pH adjusting agent is placed in a pressure vessel together with a dispersion containing polyolefin resin particles, water, a dispersant, and a dispersion aid, and the pH of the dispersion is 3 or more and 7 The pressure is adjusted to less than that, the foaming agent is charged into a pressure vessel, heated to a predetermined temperature, and under pressure, while maintaining the temperature and pressure constant, the dispersion is placed in an atmosphere at a lower pressure than in the pressure vessel. Is obtained by releasing into

  The pressure vessel to be used is not particularly limited as long as it can withstand the pressure in the vessel and the temperature in the vessel at the time of producing the pre-foamed particles, and examples thereof include an autoclave type pressure vessel.

  Examples of the blowing agent include aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane; inorganic gases such as air and nitrogen; water and the like, and these may be used alone or in combination of two or more. it can. Among these, it is preferable to use one or more selected from aliphatic hydrocarbons and water having a boiling point of 70 ° C. or less because the effect of reducing the amount of the adhering dispersant according to the present invention is remarkable.

  The amount of foaming agent used varies depending on the type of polyolefin resin used, the type of foaming agent, the target foaming ratio, etc., and cannot be specified unconditionally, but is 2 parts by weight with respect to 100 parts by weight of polyolefin resin particles. The amount is preferably 60 parts by weight or less.

  In the present invention, calcium phosphate is used as the dispersant. The calcium phosphate referred to in the present invention mainly comprises tricalcium phosphate or hydroxyapatite, and may be a mixture of the above two types. In addition to this, other calcium phosphate salts may be included.

  The amount of the dispersant used varies depending on the type and amount of the polyolefin resin particles, the foaming agent, etc., and cannot be specified in general, but is 0.2 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the polyolefin resin particles. It is preferable that the amount is 0.2 to 3.0 parts by weight.

  Dispersing aids include anionic surfactants such as sodium dodecylbenzene sulfonate, sodium n-paraffin sulfonate, sodium α-olefin sulfonate, and nonionic interfaces such as polyoxyethylene alkyl ether and polyoxyethylene sorbitan fatty acid ester. Activators, amphoteric surfactants such as alkylbetaines and alkylamine oxides, anionic polymer surfactants such as polyacrylates, polystyrene sulfonates, maleic acid α-olefin copolymer salts, and nonions such as polyvinyl alcohol Surfactants such as polymer-based surfactants can be mentioned, and these can be used alone or in combination of two or more. Among these, anionic surfactants and anionic polymer surfactants are preferable from the viewpoint of exhibiting good dispersibility, and sodium n-paraffinsulfonate is particularly preferable because of high biodegradation.

  As a combination of a dispersant and a dispersion aid, a combination of calcium phosphate and sodium n-paraffin sulfonate is preferable because of good dispersion stability.

  The amount of the dispersion aid varies depending on the type, the type and amount of the polyolefin resin to be used, the type of foaming agent, etc., and cannot be generally specified. However, the dispersion aid is usually 0.001 weight per 100 parts by weight of water. It is preferable that the amount is not less than 0.2 parts by weight. When the dispersion aid is within the above range, the dispersion of the resin particles in the pressure vessel tends to be more stable.

  Examples of the pH adjuster used in the present invention include acids such as phosphoric acid, citric acid, hydrochloric acid, nitric acid, acetic acid, boric acid, formic acid, tartaric acid, lactic acid, malic acid, and weak acid salts such as sodium dihydrogen phosphate and sodium hexametaphosphate. And strong acid salts such as magnesium sulfate, aluminum sulfate, aluminum chloride and iron nitrate can be used, and these can be used alone or in combination. Among these, it is preferable to use an acid and / or a weak acid salt because the dispersion stability of the dispersion in the pressure vessel is good, and it is preferable to use hydrochloric acid.

  The pH of the dispersion is measured by placing a predetermined amount of water, a dispersant, a dispersion aid, and a pH adjuster in a container and stirring, then collecting a part of the dispersion and measuring with a pH meter.

  The pH of the dispersion is adjusted to 3 or more and less than 7 with a pH adjuster. When the pH is lower than 3, the dissolution of calcium phosphate used as a dispersant proceeds, the dispersion state deteriorates, and polyolefin resin particles are fused together in a pressure resistant container to form large and small lumps. Most of the particles are fused. If the pH is 7 or more, the amount of dispersant adhering to the obtained polyolefin resin pre-expanded particles is large, and good fusion properties cannot be obtained when the polyolefin resin pre-expanded particles are molded.

  In order to improve the dispersibility of the polyolefin resin particles in water, it is preferable to use 100 parts by weight or more and 500 parts by weight or less of water with respect to 100 parts by weight of the polyolefin resin particles.

  The dispersion liquid comprising polyolefin resin particles, water, a dispersant, and a dispersion aid prepared in this manner in a pressure vessel is added with a foaming agent and pressurized to a predetermined pressure with stirring. After the temperature is raised to the temperature of and maintained for a certain period of time, usually 5 to 180 minutes, preferably 10 to 60 minutes, the pressurized dispersion is opened in a low pressure atmosphere by opening a valve provided in the lower part of the pressure vessel. By releasing to (usually under atmospheric pressure), polyolefin resin pre-expanded particles can be produced.

  In addition, when using the water which comprises a dispersion liquid as a foaming agent, it is preferable to pressurize inside a pressure-resistant container with inorganic gas, such as nitrogen, air, and a carbon dioxide.

  When the dispersion containing the polyolefin resin particles is discharged into a low-pressure atmosphere, it can be discharged through an opening orifice of 2 to 10 mmφ for the purpose of adjusting the flow rate and reducing variation in magnification. In some cases, the low-pressure atmosphere is filled with saturated steam for the purpose of increasing the expansion ratio.

  The temperature at which the inside of the pressure vessel is heated (hereinafter sometimes referred to as the foaming temperature) varies depending on the melting point [Tm (° C.)] of the polyolefin resin to be used, the type of foaming agent, etc. It is determined from the range of −30 (° C.) to Tm + 10 (° C.). In addition, the pressure for pressurizing the inside of the pressure vessel (hereinafter sometimes referred to as foaming pressure) varies depending on the type of polyolefin resin used, the type of foaming agent, and the desired expansion ratio of the pre-expanded particles, and cannot be specified unconditionally. Is determined from the range of approximately 1 to 8 MPa · G.

  The melting point of the polyolefin-based resin here refers to the polyolefin-based resin particles by heating the sample 5-6 mg from 40 ° C. to 220 ° C. at a rate of 10 ° C./min using a differential scanning calorimeter. From the DSC curve obtained by melting and then crystallizing by lowering the temperature from 220 ° C. to 40 ° C. at 10 ° C./min, and then increasing the temperature from 40 ° C. to 220 ° C. at 10 ° C./min. It is a value calculated | required as a melting peak temperature at the time of temperature rising.

  The polyolefin resin pre-expanded particles obtained in the present invention have a reduced amount of adhering and dispersing agent on the surface compared to the polyolefin resin pre-expanded particles obtained by the conventional method. The amount of the adhesion dispersant is preferably 700 ppm or less, more preferably 500 ppm or less.

In the present invention, the dispersant adhering to the polyolefin resin pre-expanded particles is quantified as follows. That is, the polyolefin resin pre-expanded particles obtained were dried in an oven at 60 ° C. for 24 hours, and the polyolefin resin pre-expanded particles taken out from the oven were immediately placed in a room set at a temperature of 23 ° C. and a relative humidity of 50%. Leave for hours. Next, in a room set under the same conditions, 100 g of polyolefin resin pre-expanded particles were accurately weighed to the third decimal place, and the value rounded to the third decimal place was the polyolefin resin to which the dispersant was attached. Weight of pre-expanded particles: F (g). Next, the entire amount of the polyolefin resin pre-expanded particles used for the above weight measurement is washed by immersing in 5 L of 1N hydrochloric acid aqueous solution, then immersed in 5 L of ion exchange water to wash away the hydrochloric acid solution, and then 5 L of 1 N water. After immersing and washing in an aqueous sodium oxide solution, the sodium hydroxide is washed by immersing in 5 L of ion exchange water. After this operation is repeated twice, the entire amount of polyolefin resin pre-expanded particles is dried in an oven at 60 ° C. for 24 hours, then taken out of the oven and immediately left in a room set at 23 ° C. and 50% relative humidity for 72 hours. Subsequently, in a room set under the same conditions, the weight of the polyolefin resin pre-expanded particles: S (g) is obtained in the same manner as described above. The difference between the weight: F and the weight: S is defined as the amount of the dispersant adhering to the surface of the polyolefin resin pre-expanded particles, and the amount of adhering to the polyolefin resin pre-expanded particles to which the dispersant is adhering is adopted.
Adhesive dispersant amount (ppm) = (FS) / F × 10 ⁶

  The polyolefin-based resin pre-expanded particles obtained as described above can be made into a polyolefin-based resin expanded molded body by a conventionally known molding method. For example, a) Pre-expanded particles are pressurized with an inorganic gas, such as air or nitrogen, impregnated with the inorganic gas in the pre-expanded particles to give a predetermined internal pressure of the pre-expanded particles, filled in a mold, (B) A method in which pre-expanded particles are compressed by gas pressure and filled in a mold, and a heat-fusing method is carried out with steam using the recovery force of the pre-expanded particles. A method such as a method in which pre-expanded particles are filled in a mold without being heated and heat-sealed with water vapor can be used.

  Since the polyolefin resin pre-expanded particles of the present invention have a small amount of adhering dispersant, the polyolefin resin foam molded article obtained from the polyolefin resin pre-expanded particles has good fusion properties. Therefore, it can be suitably used for applications requiring strength and weight reduction, for example, automobile members such as cushioning packaging materials and bumper core materials.

  Next, the manufacturing method of the polyolefin resin pre-expanded particles of the present invention will be described in detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

<Measurement of melt flow index>
The melt flow index (MI) was measured using an MI measuring instrument described in JIS K7210, with an orifice of 2.0959 ± 0.005 mmφ, an orifice length of 8.000 ± 0.025 mm, a load of 2160 g, and 230 ± 0.2 ° C. Performed under conditions.

<Dispersion stability in pressure vessel>
The dispersion stability in the pressure vessel was evaluated by the following index. That is, the polyolefin resin particles dispersed in an aqueous dispersion medium in a pressure vessel are converted into a melting point [T
m (° C.)], when heated to a temperature of Tm−30 (° C.) to Tm + 10 (° C.), the inside of the pressure-resistant container became impossible to stir and could not be pre-foamed. For the case, the state of the polyolefin resin particles remaining in the pressure vessel after preliminary foaming was observed, and the one in which a lump was formed in the pressure vessel was Δ, and about 2 to 3 resin particles were adhered. If the resin remained only, the dispersibility was good, and if all of the resin particles were not adhered, the dispersibility was good, and ◎.

<Bending elastic modulus>
The flexural modulus was measured according to JIS K7106.

<Apparent density>
The polyolefin resin pre-expanded particles are put in a 10 L container, and the weight (g) of the pre-expanded particles in the container is measured. The obtained weight was divided by the container capacity (L) to obtain an apparent density (g / L).

<Adhesive dispersant amount>
The obtained polyolefin resin pre-foamed particles were washed with water, dried in an oven at 60 ° C. for 24 hours, and then taken out of the oven, the polyolefin resin pre-foamed particles were immediately placed in a room set at a temperature of 23 ° C. and a relative humidity of 50%. Leave for 72 hours. Next, in a room set under the same conditions, 100 g of polyolefin resin pre-expanded particles were accurately weighed to the third decimal place, and the value rounded to the third decimal place was the polyolefin resin to which the dispersant was attached. Weight of pre-expanded particles: F (g). Next, the entire amount of the foamed particles used for the above weight measurement is immersed in 5 L of 1N aqueous hydrochloric acid and washed, then immersed in 5 L of ion exchange water to wash out the hydrochloric acid solution, and then into 5 L of 1 N aqueous sodium hydroxide. After immersing and washing, sodium hydroxide is washed by immersing in 5 L of ion exchange water. After repeating this operation twice, the entire amount of the expanded particles is dried in an oven at 60 ° C. for 24 hours, then taken out of the oven and immediately left in a room set at 23 ° C. and 50% relative humidity for 72 hours. Subsequently, in a room set under the same conditions, the weight of the polyolefin resin pre-expanded particles: S (g) is obtained in the same manner as described above. The difference between weight: F and weight: S was defined as the amount of dispersant adhering to the surface of the polyolefin resin pre-expanded particles.

<Evaluation of fusion rate of foamed molded product>
A polyolefin-based resin foam molded body obtained by molding with a 400 × 300 × 60 mm mold is cut with a cutter knife in the thickness direction of the foam molded body, and then the foam molded body is manually removed from the cut portion. Break. The fracture surface was observed and the ratio of the foamed particles destroyed was determined.

Example 1
As a base resin, MI = 7/10 min, melting point 143 ° C., flexural modulus 800 MPa, ethylene-propylene random copolymer containing 3.6 wt% of ethylene as a comonomer, talc 0 as a cell nucleating agent The ethylene-propylene random copolymer and talc were dry blended using 0.03 part by weight. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.8 mg / grain.

100 parts by weight (2 kg) of the obtained polypropylene resin particles, 283 parts by weight of water, 1.07 parts by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Industrial Co., Ltd.) as a dispersing agent, and 0.044 parts by weight of sodium alkyl sulfonate as a dispersing aid Part was placed in a pressure-resistant autoclave having a volume of 0.01 m ³ and the pH of the dispersion was adjusted to 5.9 with 1N hydrochloric acid, and then 18 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated to a foaming temperature of 137 ° C. Thereafter, isobutane was additionally injected to increase the pressure in the autoclave to a foaming pressure of 1.9 MPa · G. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened and a 4.0 mmφ opening orifice was passed through. The contents of the autoclave were released under atmospheric pressure to obtain polypropylene resin pre-expanded particles. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.26 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 1.

（実施例２）
基材樹脂として、ＭＩ＝６／１０分、融点１４６℃、曲げ弾性率１０００ＭＰａ、コモノマーとしてエチレンを２．８ｗｔ％含むエチレン−プロピレンランダム共重合体１００重量部に対し、カーボンブラックを４重量部、更にセル造核剤としてタルク０．０３重量部用いて、前記エチレン−プロピレンランダム共重合体とカーボンブラックとタルクをドライブレンドした。ドライブレンドした混合物を押出機内で溶融混練し円形ダイよりストランド状に押出し、水冷後、カッターで切断し、一粒の重量が１．２ｍｇ／粒のポリプロピレン系樹脂粒子を得た。

(Example 2)
As a base resin, MI = 6/10 minutes, melting point 146 ° C., flexural modulus 1000 MPa, 4 parts by weight of carbon black with respect to 100 parts by weight of ethylene-propylene random copolymer containing 2.8 wt% of ethylene as a comonomer, Further, 0.03 part by weight of talc was used as a cell nucleating agent, and the ethylene-propylene random copolymer, carbon black and talc were dry blended. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand form from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.2 mg / grain.

100 parts by weight (2 kg) of the obtained polypropylene resin particles, 200 parts by weight of water, 1.12 parts by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a dispersing agent, 0.031 weight by weight of sodium alkyl sulfonate as a dispersing aid Part was placed in a pressure-resistant autoclave having a volume of 0.01 m ³ , and the pH of the dispersion was adjusted to 6.0 with 1N hydrochloric acid, and 13 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated and heated to a foaming temperature of 141 ° C. Thereafter, isobutane was additionally injected to increase the pressure in the autoclave to a foaming pressure of 1.9 MPa · G. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened and a 4.0 mmφ opening orifice was passed through. The contents of the autoclave were released under atmospheric pressure to obtain polypropylene resin pre-expanded particles. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.28 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 1.

(Example 3)
Pre-expanded particles were obtained in the same manner as in Example 2 except that the pH of the dispersion was adjusted to 5.0, and heated and fused under the same conditions as in Example 2 to obtain a foamed molded product. The evaluation results are shown in Table 1.

Example 4
Prefoamed particles were obtained in the same manner as in Example 2 except that the pH of the dispersion was adjusted to 3.3 with 6N hydrochloric acid, and heated and fused under the same conditions as in Example 2 to obtain a foamed molded product. The evaluation results are shown in Table 1.

  From the results of Examples 1 to 4, in the region where the pH is 3 or more and less than 7, the amount of the surface-attached dispersant of the polypropylene resin pre-foamed particles can be reduced without impairing the dispersion stability in the autoclave, and foaming can be achieved. The fusion of the molded body was improved.

(Example 5)
As a base resin, MI = 6/10 minutes, melting point 146 ° C., flexural modulus 1000 MPa, ethylenebispropylamide 2% with respect to 100 parts by weight of ethylene-propylene random copolymer containing 2.8 wt% ethylene as a comonomer. The ethylene-propylene random copolymer, ethylenebisstearic acid amide, and talc were dry blended using 0.0 part by weight and 0.03 part by weight of talc as a cell nucleating agent. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.8 mg / grain.

100 parts by weight (1.8 kg) of the obtained polypropylene resin particles, 269 parts by weight of water, 1.39 parts by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a dispersing agent, and sodium alkyl sulfonate as a dispersing aid 0. 03 parts by weight was charged into a pressure-resistant autoclave having a capacity of 0.01 m ³ , and the pH of the dispersion was adjusted to 6.0 with 1N hydrochloric acid, and then 20 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated to a foaming temperature of 133 ° C. Thereafter, isobutane was additionally injected to increase the pressure in the autoclave to a foaming pressure of 2.2 MPa · G. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened and a 4.0 mmφ opening orifice was passed through. The contents of the autoclave were released under atmospheric pressure to obtain polypropylene resin pre-expanded particles. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.28 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 1.

  From the results of Examples 2 to 5, the amount of the surface adhering dispersant of the polypropylene resin pre-expanded particles is reduced without impairing the dispersion stability even if additives such as carbon black and ethylene bis stearamide are contained. Can do.

(Example 6)
As a base resin, MI = 6/10 minutes, melting point 146 ° C., flexural modulus 1000 MPa, ethylene-propylene random copolymer containing 2.8 wt% of ethylene as a comonomer, melamine (manufactured by BASF) The ethylene-propylene random copolymer, melamine and talc were dry blended using 0.5 parts by weight and further 0.3 parts by weight of talc as a cell nucleating agent. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand form from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.2 mg / grain.

100 parts by weight (2.4 kg) of the obtained polypropylene resin particles, 200 parts by weight of water, 0.8 part by weight of tricalcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a dispersing agent, and sodium alkyl sulfonate as a dispersing aid 0. 01 parts by weight was charged into a pressure-resistant autoclave having a volume of 0.01 m ³ , and the pH of the dispersion was adjusted to 6.1 with 1N hydrochloric acid, followed by stirring. The temperature of the autoclave is raised and heated to a foaming temperature of 154 ° C., then compressed air is injected to adjust the inside of the autoclave to a foaming pressure of 2.0 MPa · G, and the polypropylene resin particles are impregnated with water. After holding at the foaming temperature and foaming pressure for 30 minutes, the valve at the bottom of the autoclave is opened, and the autoclave contents are released under atmospheric pressure with the atmospheric temperature adjusted to 100 ° C. through a 4.0 mmφ opening orifice. Thus, polypropylene resin pre-expanded particles were obtained. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.28 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 1.

  From the results of Example 6, even when water is used as the foaming agent, the amount of the surface adhering dispersant of the pre-foamed particles can be reduced without impairing the dispersion stability in the autoclave, and the foamed molded product can be fused. Improved.

(Example 7)
As a base resin, MI = 6/10 minutes, melting point 146 ° C., flexural modulus 1000 MPa, ethylene propylstearic acid amide was added to 100 parts by weight of an ethylene-propylene random copolymer containing 2.8 wt% of ethylene as a comonomer. The ethylene-propylene random copolymer, ethylenebisstearic acid amide, and talc were dry blended using 2.0 parts by weight and further 0.03 part by weight of talc as a cell nucleating agent. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand form from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.2 mg / grain.

100 parts by weight (1.8 kg) of the obtained polypropylene resin particles, 269 parts by weight of water, 1.39 parts by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a dispersing agent, and sodium alkyl sulfonate as a dispersing aid 0. 03 parts by weight was charged into a pressure-resistant autoclave having a capacity of 0.01 m ³ , and the pH of the dispersion was adjusted to 4.6 with sodium dihydrogen phosphate. Then, 20 parts by weight of isobutane was added as a blowing agent with stirring. The temperature of the autoclave is raised and heated to a foaming temperature of 133 ° C., and then isobutane is additionally injected to adjust the inside of the autoclave to a foaming pressure of 2.2 MPa · G. After holding, the valve at the bottom of the autoclave was opened, and the autoclave contents were discharged under atmospheric pressure through an opening orifice of 4.0 mmφ to obtain polypropylene resin pre-expanded particles. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.28 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 1.

(Example 8)
Pre-expanded particles were obtained in the same manner as in Example 7, except that the pH of the dispersion was adjusted to 5.6 with citric acid, and heated and fused under the same conditions as in Example 7 to obtain a foamed molded product. The evaluation results are shown in Table 1.

Example 9
Base resin: MI = 2/10 min, melting point 123 ° C., 100 parts by weight of linear low density polyethylene containing 8.2% by weight of 4-methylpentene as comonomer, 0.03 wt.% Of talc as cell nucleating agent Part of the linear low density polyethylene and talc were dry blended. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand form from a circular die, cooled with water, and cut with a cutter to obtain polyethylene resin particles having a weight of 1.8 mg / grain.

100 parts by weight (2.0 kg) of the obtained polyethylene resin particles, 232 parts by weight of water, 1.38 parts by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a dispersing agent, and sodium alkyl sulfonate as a dispersing aid 0. 01 parts by weight was charged into a pressure-resistant autoclave having a volume of 0.01 m ³ , and the pH of the dispersion was adjusted to 6.0 with 1N hydrochloric acid, and then 13 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated to a foaming temperature of 117 ° C. Thereafter, isobutane was additionally injected to increase the pressure in the autoclave to a foaming pressure of 1.9 MPa · G, and after maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened and a 4.0 mmφ opening orifice was passed through. The autoclave contents were discharged under atmospheric pressure to obtain polyethylene resin pre-expanded particles. The obtained pre-expanded particles were filled in a 400 × 300 × 60 mm mold and heated and fused with steam at a molding temperature of 0.10 MPa · G to obtain a foamed molded product. The evaluation results are shown in Table 1.

(Example 10)
Using Evertate F1103-1 (manufactured by Sumitomo Chemical Co., Ltd.), which is a polyethylene resin, 0.2 parts by weight of talc is mixed with 100 parts by weight of polyethylene resin, melt-mixed in an extruder, granulated, and submerged in water. By cutting immediately after extrusion, spherical polyethylene resin particles having a particle weight of about 1 mg / particle were produced.

Subsequently, in a 0.006 m ³ autoclave, 150 parts by weight of water, 1.0 part by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.), 0.024 part by weight of α-olefin sulfonic acid sodium, and 30 parts by weight of polyethylene resin particles are added. Suspended, 15 parts by weight of styrene, 0.26 parts by weight of benzoyl peroxide (10 hours half-life temperature: 74 ° C.) as a polymerization initiator, and t-butyl peroxybenzoate (10 hours half) as a radical species-generating crosslinking agent (Phase temperature: 104 ° C.) A solution in which 0.60 part by weight was dissolved was added. Thereafter, this aqueous suspension was heated to 70 ° C. and maintained for 30 minutes to impregnate the polyethylene resin particles with the styrene monomer solution. The temperature is further raised to 85 ° C., 55 parts by weight of a styrene monomer is dropped into the reaction system over 3 hours and 40 minutes, polymerization is performed, the temperature is further raised to 125 ° C. and held for 30 minutes, cooled, washed and dehydrated -Styrene-modified polyethylene resin particles were obtained by drying. The amount of crosslinking agent decomposed at this point was 26%.

100 parts by weight (0.75 kg) of the obtained styrene-modified polyethylene resin particles, 150 parts by weight of water, 2.0 parts by weight of tricalcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a dispersant, and alkylsulfonic acid as a dispersion aid 0.01 parts by weight of sodium was charged in a pressure-resistant autoclave having a capacity of 0.0045 m ³ , the pH of the dispersion was adjusted to 6.0 with 1N hydrochloric acid, and then 20 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated and heated to a foaming temperature of 140 ° C. After holding at 1.8 MPa · G for 30 minutes, the valve at the bottom of the autoclave is opened, and the autoclave contents are discharged under atmospheric pressure through an opening orifice of 4.0 mmφ to obtain styrene-modified polyethylene resin pre-expanded particles. It was. The obtained styrene-modified polyethylene resin pre-foamed particles were washed, dehydrated and dried, cured at room temperature for 2 days, and then filled in a 400 × 300 × 60 mm mold, and a molding temperature of 0.10 MPa · G It was heated and fused with the above steam to obtain a foamed molded product.

(Example 11)
Polyether-polyolefin resin block with respect to 100 parts by weight of ethylene-propylene random copolymer containing MI = 6/10 min, melting point 146 ° C., flexural modulus 1000 MPa, ethylene 2.8 wt% as comonomer as base resin 10 parts by weight of a copolymer (trade name: Pelestat 303, manufactured by Sanyo Kasei Co., Ltd.) and 0.03 parts by weight of talc as a cell nucleating agent, and the ethylene-propylene random copolymer, melamine and talc are dry blended. did. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand form from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.2 mg / grain.

100 parts by weight (1.8 kg) of the obtained polypropylene resin particles, 269 parts by weight of water, 1.5 parts by weight of tribasic calcium phosphate (manufactured by Taihei Chemical Industrial Co., Ltd.) as a dispersing agent, and sodium alkyl sulfonate as a dispersing aid 0. 04 parts by weight was charged into a pressure-resistant autoclave having a volume of 0.01 m ³ , and the pH of the dispersion was adjusted to 5.6 with 1N hydrochloric acid, and then 18 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated and heated to a foaming temperature of 140 ° C. Thereafter, isobutane is additionally injected and the pressure inside the autoclave is increased to a foaming pressure of 2.0 MPa · G. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave is opened and a 4.0 mmφ opening orifice is passed through. The contents of the autoclave were released under atmospheric pressure to obtain polypropylene resin pre-expanded particles. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.28 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 1.

(Comparative Example 1)
Except that the pH of the dispersion was not adjusted, pre-expanded particles were obtained in the same manner as in Example 1, and heated and fused under the same conditions as in Example 1 to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 2)
Pre-expanded particles were obtained by the same method as in Example 2 except that the pH of the dispersion was not adjusted, and heated and fused under the same conditions as in Example 2 to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 3)
The same procedure as in Example 2 was performed, except that the pH of the dispersion was adjusted to 2.8 using 6N hydrochloric acid. The evaluation results are shown in Table 2.

(Comparative Example 4)
Pre-expanded particles were obtained in the same manner as in Example 5 except that the pH of the dispersion was not adjusted, and heated and fused under the same conditions as in Example 5 to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 5)
Except that the pH of the dispersion was not adjusted, pre-expanded particles were obtained in the same manner as in Example 6, and heated and fused under the same conditions as in Example 6 to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 6)
Pre-expanded particles were obtained by the same method as in Example 9 except that the pH of the dispersion was not adjusted, and heated and fused under the same conditions as in Example 9 to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 7)
As base resin, MI = 7/10 min, melting point 143 ° C., flexural modulus 800 MPa, 100 parts by weight containing 3.6 wt% ethylene as comonomer, and 00.3 parts by weight talc as cell nucleating agent, The ethylene-propylene random copolymer and talc were dry blended. The dry blended mixture was melt-kneaded in an extruder, extruded into a strand from a circular die, cooled with water, and cut with a cutter to obtain polypropylene resin particles having a weight of 1.8 mg / grain.

100 parts by weight (1.5 kg) of the obtained polypropylene resin particles, 300 parts by weight of water, 0.30 part by weight of kaolin (manufactured by Engelhard) as a dispersant, and 0.006 part by weight of dodecylbenzenesulfonic acid as a dispersion aid. Into a pressure-resistant autoclave having a capacity of 0.01 m ³ , 18 parts by weight of isobutane was added as a blowing agent with stirring. The autoclave contents were heated to a foaming temperature of 137 ° C. Thereafter, isobutane was additionally injected to increase the pressure in the autoclave to a foaming pressure of 1.9 MPa · G, and after maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened and a 4.0 mmφ opening orifice was passed through. The contents of the autoclave were released under atmospheric pressure to obtain polypropylene resin pre-expanded particles. The pre-expanded particles obtained were impregnated with air by air pressure treatment to give an internal pressure of 0.08 to 0.10 MPa · G, and then filled into a 400 × 300 × 60 mm mold, and 0.26 MPa · It was heated and fused with steam having a molding temperature of G to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 8)
Except that the pH of the dispersion was adjusted to 6.0 with 1N hydrochloric acid, pre-expanded particles were obtained in the same manner as in Comparative Example 7, and fused under the same conditions as in Comparative Example 7 to obtain a foamed molded product. The evaluation results are shown in Table 2.

  From Comparative Examples 7 and 8, it was found that the effect of the present invention was small when kaolin was used as the dispersant.

(Comparative Example 9)
Except that the pH of the dispersion was not adjusted, pre-expanded particles were obtained in the same manner as in Example 10, and fused under the same conditions as in Example 10 to obtain a foamed molded product. The evaluation results are shown in Table 2.

(Comparative Example 10)
Except that the pH of the dispersion was not adjusted, pre-expanded particles were obtained in the same manner as in Example 11, and fused under the same conditions as in Example 11 to obtain a foamed molded product. The evaluation results are shown in Table 2.

Claims (6)

A dispersion liquid containing a polyolefin resin particle, water, a dispersant, a dispersion aid and a foaming agent are placed in a pressure vessel, and the pressure vessel is heated to a predetermined temperature under pressure. In the method of obtaining the polyolefin resin pre-expanded particles by discharging the dispersion under a lower pressure atmosphere than in the pressure vessel while keeping constant, calcium phosphate is used as a dispersant, and the pH of the dispersion in the pressure vessel is adjusted to pH. A method for producing polyolefin resin pre-expanded particles , which is adjusted to 3 or more and less than 7 with a regulator. The method for producing polyolefin resin pre-expanded particles according to claim 1 , wherein the pH of the dispersion in the pressure vessel is adjusted to 3 or more and 6 or less with a pH adjuster. pH adjusting agent, an acid and / or a weak acid salt, the manufacturing method of polyolefin resin pre-expanded particles according to claim 1 or 2. As a blowing agent, boiling point of 70 ° C. or less of aliphatic hydrocarbons, use at least one member selected from water, producing a polyolefin resin pre-expanded particles according to any one of claims 1 to 3. The manufacturing method of the polyolefin resin pre-expanded particle as described in any one of Claims 1-4 whose amount of dispersing agent adhering to the polyolefin resin pre-expanded particle is 700 ppm or less with respect to the polyolefin resin pre-expanded particle. The polyolefin resin pre-expanded particles obtained by the production method according to any one of claims 1-5, obtained by heating was filled into the mold, producing a polyolefin resin foam molded article.