JP5326583B2 - Method for producing polyolefin resin block-like foam molded article - Google Patents

Description

The present invention relates to a method for producing a polyolefin resin block-like foamed molded article by filling polyolefin resin expanded particles into a mold cavity and foaming and fusing them with steam.

  Conventionally, in order to supply steam into a mold cavity (molding space), a mold in which foamed polyolefin resin foam particles are filled into a mold and foamed and fused with steam to produce a block-shaped foamed molded product. The steam holes are generally provided, and steam is supplied into the mold cavity through these steam holes to heat, foam and fuse the polyolefin resin foam particles. Such a vapor hole is called a slit or a core vent and is made of a cylindrical member having a diameter of about φ3 mm to φ10 mm, in which a slit-like narrow groove of 0.3 to 0.5 mm is formed, or φ0 It is common to use a plurality of pores with a diameter of 3 mm to φ0.5 mm, which prevents foam particles from leaking into the steam chamber while introducing steam into the mold cavity. ing.

  However, since the thickness of the foamed molded product is often relatively large, the opening ratio is limited in the steam supply from the core vent alone, and therefore the thickness of the foamed molded product, particularly the foamed molded product, is limited. There has been a problem that the expanded olefin resin particles in the vicinity of the center part of the slag were not foamed and fused, resulting in defective products.

  As a technique for improving poor fusion, there is a technique related to the shape of a vapor hole when foamed particles having a particle size of about 0.4 mm to 0.9 mm are used. This is because the steam hole is provided in a slit shape, the maximum opening width of the slit groove is 0.8 mm or less, and at least the opening ratio of the movable surface and its facing surface is 4 to 25% to obtain a high fusion rate. It is related with the foaming resin block manufacturing metal mold | die for disappearance models (patent document 1).

  Further, as a method for increasing the aperture ratio and improving the filling property of the pre-expanded particles, in a foaming mold having a mold cavity and a steam chamber formed so as to surround the mold cavity, the mold cavity and the steam chamber A technique is disclosed in which at least a part of a partition wall portion is formed by a partition plate in which a plurality of rod-shaped partition members are arranged in parallel to each other (Patent Document 2). However, an opening area for supplying steam can be ensured by forming a mold with a partition plate in which a plurality of rod-shaped partition members are arranged in parallel with each other. It has been found that when molding is performed using resin foam particles, there is a problem that shrinkage and deformation occur at the end of the foam molded article, resulting in dimensional defects.

JP 2002-264163 A Japanese Utility Model Publication No. 2-108019

The object of the present invention and the problem to be solved are that, in the production of a block-like foam molded article using olefin resin foam particles, there is no occurrence of shrinkage or deformation while maintaining a good fusion rate inside the foam molded article. Another object of the present invention is to provide a method capable of producing a polyolefin-based resin block-like foam molded article having excellent dimensional stability.

  As a result of intensive research to solve the above-mentioned problems, the present inventor has increased the opening ratio of the vapor holes in at least one of the front and back surfaces of the mold 6 constituting the mold cavity from the inside to the end. The inventors have found that a block-shaped foamed molded article having excellent dimensional stability can be obtained while ensuring a high fusion rate at the center of the foamed molded article by setting the vapor hole opening ratio to a sufficient level.

That is, the present invention relates to a manufacturing method and a polyolefin resin block foamed molded article of the following polyolefin resin block foamed molded article.
(1) A mold that forms a mold cavity in a mold for filling a polyolefin resin foam particle into a mold cavity and foaming and fusing the polyolefin resin foam particle with steam to produce a block-shaped foam molded article Among the six surfaces, the opening ratio of the vapor holes in the four mold surfaces corresponding to the upper surface, the lower surface, and the left and right side surfaces of the block-shaped foamed molded product is 0.5% or more and 5% or less, and the surface of the block-shaped foamed molded product In addition, in at least one of the two mold surfaces corresponding to the back surface, the opening ratio of the steam holes at the end is 0.5% or more and 5% or less, and the opening ratio of the steam holes in the inner part is 7% or more. 30% or less, and the mold surface of the inner portion using a plurality of rod-shaped member via a predetermined gap is composed of a member arranged in parallel lube lock-shaped molded foam product manufacturing mold, the mold fossa Filled with polyolefin resin foam particles in the mold Process for producing a polyolefin resin block foamed molded article, characterized by foam molding. .
(2) The end of at least one mold surface of the two mold surfaces corresponding to the front and back surfaces of the block-like foamed molded body in the mold is within 100 mm from the mold end surface. The manufacturing method of the polyolefin resin block-shaped foaming molding as described in (1) .
(3) In the member in which the plurality of rod-shaped members are arranged in parallel through a certain gap, the width of the plurality of rod-shaped members is 2 mm or more and 4 mm or less, and the gap for arranging these rod-shaped members is 0.25 mm or more and 0.75 mm. The method for producing a polyolefin-based resin block-shaped foam molded article according to (1) or (2), characterized in that:
(4) The polyolefin resin block according to any one of (1) to (3), wherein a member in which the plurality of rod-shaped members are arranged in parallel with a predetermined gap is made of stainless steel. For producing a foamed molded article .
( 5 ) A mold that forms a mold cavity in a mold for filling a polyolefin resin foam particle into a mold cavity and foaming and fusing the polyolefin resin foam particle with steam to produce a block-shaped foam molded article Among the six surfaces, the opening ratio of the vapor holes in the four mold surfaces corresponding to the upper surface, the lower surface, and the left and right side surfaces of the block-shaped foamed molded product is 0.5% or more and 5% or less, and the surface of the block-shaped foamed molded product In addition, in at least one of the two mold surfaces corresponding to the back surface, the opening ratio of the steam holes at the end is 0.5% or more and 5% or less, and the opening ratio of the steam holes in the inner part is 7% or more. 30% or less, and block the mold surface of the inner portion are obtained using configured block-shaped molded foam product manufacturing mold of a member arranged a plurality of bar-like members in parallel through a fixed gap Foamed molded body, block-shaped Convex portions that are vapor hole traces on the upper surface, lower surface, and left and right side surfaces of the foam molded body are 0.5% to 5%, and at least one of the two surfaces corresponding to the front and back surfaces of the block-shaped foam molded body. The polyolefin resin block-like foamed molded article is characterized in that the convex portion, which is a vapor hole trace on the inner side, is 7% or more and 30% or less.

  The mold of the present invention has a small aperture ratio at the end of the mold cavity, and a large aperture ratio at portions other than the end. Accordingly, excessive steam does not flow through the mold cavity end where deformation and contraction are likely to occur, and sufficient steam flows through the inner portion where poor fusion is likely to occur. Therefore, when the mold of the present invention is used, it is possible to obtain a block-shaped foamed molded article in which foamed particles are sufficiently fused without deformation and contraction.

  In addition, when the mold of the present invention is used, when the foam particles are filled into the mold by the air flow, the air flow is homogenized in the same manner as the flow of the steam, so the foam particles are uniformly filled. The For this reason, it is possible to obtain a foamed molded article having a low density distribution.

  Furthermore, since the mold of the present invention has a large opening ratio of the steam holes in the inner part of at least one of the two surfaces corresponding to the front and back surfaces of the block-shaped foamed molded article, the amount of air and steam is greatly increased. Particle filling time and steam heating time can be shortened, and the molding cycle can be shortened.

  Conventionally, it has often been necessary to maintain and clean the mold in order for the resin powder adhering to the surface of the polyolefin resin expanded particles to block the slit of the core vent. However, in the mold according to the present invention in which the opening ratio is remarkably increased, a sufficient opening ratio can be maintained even when the steam hole is slightly blocked, so the extension or the number of times until maintenance is reduced. Is possible.

It is sectional drawing which shows an example of the metal mold | die of this invention. It is a perspective view of the foaming molding manufactured with the metal mold | die of this invention. It is a front view of the middle mold 4b of FIG. It is a perspective view which shows an example of the member which has arranged the several rod-shaped member in parallel.

  FIG. 1 shows an example of a mold for producing a block-shaped foamed molded product of the present invention. The mold shown in FIG. 1 includes a fixed mold 1a and a movable mold 1b.

  The fixed die 1a includes a frame 2a, a center plate 3a attached to the frame 2a, and a middle die 4a attached to the center plate 3a. The middle mold 4a includes an upper member 5a, a lower member 5a ', a vertical member 6a, and left and right side members (not shown). A feeder 15 for supplying pre-expanded particles to the mold is attached to the vertical member 6a. A steam chamber 9a is formed by the middle mold 4a and the frame 2a. A steam valve 10a and a drain valve 11a are connected to the steam chamber 9a.

  The movable mold 1b includes a frame 2b, a center plate 3b attached to the frame 2b, and a middle mold 4b attached to the center plate 3b. The middle mold 4b includes an upper member 5b, a lower member 5b ', a vertical member 6b, and left and right side members (not shown). The vertical member 6b includes an end portion 7b and an inner portion 8b. Also in the movable mold 1b, a steam chamber 9b is formed by the middle mold 4b and the frame 2b. A steam valve 10b and a drain valve 11b are connected to the steam chamber 9b.

  The mold cavity 12 is formed by the middle mold 4a and the middle mold 4b. The mold cavity 12 is filled with foam particles and the filled foam particles are heated by steam or the like, and further expanded to fuse the foam particles together to produce a foam molded article. The shape of the mold cavity 12 is the shape of a block-like foamed molded product to be molded.

  FIG. 2 is a perspective view of a foamed molded product manufactured by the mold of FIG. The exposed surface of the vertical member 6a of the middle mold 4a to the mold cavity 12 side corresponds to the surface of the foam molded body, and the exposed surface of the vertical member 6b of the middle mold 4b to the mold cavity side corresponds to the back surface of the foam molded body. The exposed surface of the upper member 5a of the middle mold 4a on the mold cavity 12 side corresponds to the upper surface of the foam molded article. The exposed surface of the lower member 5a 'of the middle mold 4a toward the mold cavity 12 corresponds to the lower surface of the foam molded article. In addition, the exposed surfaces of the left and right side members of the middle mold 4a (not shown) toward the mold cavity 12 correspond to the left and right side surfaces of the foamed molded body.

  In the mold of the present invention, among the 6 mold surfaces constituting the mold cavity, the opening ratios on 4 surfaces corresponding to the upper and lower surfaces and the left and right side surfaces of the block-shaped foamed molded product are 0.5% or more and 5% or less. When the opening ratio in this portion is less than 0.5%, the fusion of the foamed particles on the side surface of the foamed molded article becomes insufficient. On the other hand, when the opening ratio exceeds 5%, deformation and shrinkage occur in the foamed molded article, and the dimensional stability is lowered. The aperture ratio refers to the ratio of the opening to the exposed surface of the middle mold 4a and the middle mold 4b on the mold cavity 12 side.

  There is no restriction | limiting in particular in the formation method of an opening part, You may form by a core vent or a drill hole, and you may form a slit directly in the member which comprises the middle mold 4a and the middle mold 4b. Further, a member in which a plurality of rod-shaped members are arranged in parallel at a constant interval may be used. In any case, the aperture ratio is 0.5% or more and 5% or less.

  In the mold of the present invention, the opening rate of the steam holes at the end is 0 on at least one of the two surfaces corresponding to the front surface and the back surface of the block-shaped foamed molded body among the six surfaces constituting the mold cavity. It is 5% or more and 5% or less, and the opening ratio of the vapor holes in the inner part is 7% or more and 30% or less. Specifically, in the mold of FIG. 1, this condition is satisfied by making the opening ratio of the end portion 7b of the vertical member 6b of the middle mold 4b smaller than the opening ratio of the inner portion 8b. That is, the opening ratio of the end portion 7b is 0.5% or more and 5% or less, and the opening ratio of the inner portion 8b is 7% or more and 30% or less. FIG. 3 shows a front view of the middle die 4b. In FIG. 3, 7b is an end. Reference numeral 13 denotes a slit formed at the end, and reference numeral 14 denotes a gap between the plurality of rod-shaped members.

  In the mold of FIG. 1, the opening ratio of the end 7 b in the vertical member 6 b of the middle mold 4 b is smaller than the opening ratio of the inner part 8 b, but the opening ratio is small at the end of the vertical member 6 a of the middle mold 4 a. There are no examples shown. However, the opening ratio of the end portion of the vertical member 6a of the middle mold 4a may be 0.5% or more and 5% or less. In this case, an aspect similar to that of the middle mold 4b in FIG. 1 may be adopted. However, the vertical member 6b of the middle mold 4b is not provided with an end portion having a small aperture ratio, and the opening ratio of the vertical member 6a of the middle mold 4a is 0.5% or more. It is good also as an aspect which provided the edge part made 5% or less.

  When the opening ratio of the end portion is less than 0.5%, the fusion of the foamed particles on the back surface of the foamed molded product becomes insufficient. On the other hand, when the opening ratio of the end portion exceeds 5%, deformation and shrinkage occur at the end portion of the foamed molded article, and the dimensional stability is lowered. When the opening ratio of the inner portion is less than 7%, the fusion of the central portion in the thickness direction of the foamed molded article becomes insufficient. In a conventional mold structure using a core vent, the strength of the mold decreases when the opening ratio of the inner side exceeds 30%.

  In the mold of the present invention, the inner mold surface of at least one of the two surfaces corresponding to the front surface and the back surface of the block-shaped foamed molded article has a plurality of rod-shaped members arranged in parallel with a certain gap. It is comprised from the member which did. By using a member in which a plurality of rod-shaped members are arranged in parallel through a certain gap, a mold having mechanical strength can be manufactured even if the aperture ratio is large. FIG. 4 shows an example of a member in which a plurality of rod-like members are arranged in parallel with a certain gap. Although the magnitude | size of a rod-shaped member is not specifically limited, It is preferable that width is 2 mm or more and 4 mm or less. The fixed gap may be an interval at which the foam particles filling the mold cavity do not leak out of the mold cavity. This interval is determined by the size of the expanded particles to be used, but this interval is usually preferably 0.1 mm or more and 2.0 mm or less, and more preferably 0.25 mm or more and 0.75 mm or less.

  There is no particular limitation on the cross-sectional shape of the rod-shaped member, but when a plurality of rod-shaped members are arranged in parallel through a certain gap, a shape in which the aperture ratio of one surface is small and the aperture ratio of the other surface is large Is preferred. Examples of such cross-sectional shapes include triangles and trapezoids. FIG. 4 shows an example of a member in which rod-shaped members having a triangular cross section are arranged in parallel with a certain gap, and the opening ratio of the upper surface is smaller than the opening ratio of the lower surface. In the mold shown in FIG. 1, the inner portion 8b of the vertical member 6b of the middle die 4b is formed of a member in which a plurality of rod-shaped members having a triangular cross section are arranged in parallel. Further, the entire vertical member 6a of the middle mold 4a is composed of a member in which a plurality of bar members having a triangular cross section are arranged in parallel.

  If a member in which rod-like members having a triangular or trapezoidal cross section are arranged in parallel through a certain gap is used, fluid such as steam or water tends to easily circulate and the heating and cooling efficiency tends to be improved. Such a member is called a wedge wire and is commercially available.

  The material of the rod-shaped member is not particularly limited, but stainless steel is preferable because it is difficult to corrode and is easily available. Moreover, if stainless steel is used, the resin powder can be easily removed. In the middle mold 4a and the middle mold 4b, it is preferable to use aluminum for portions other than the members in which the rod-shaped members are arranged in parallel with a certain gap.

  There is no particular limitation on the size of the mold. The size of the mold cavity is almost the size of a foam molded article, and a foam molded article having a size of about 1200 mm × 1000 mm × 200 mm can be manufactured. The block-shaped foamed molded product of the present invention refers to a foamed molded product having a thickness of 20 mm to 300 mm, preferably 40 mm to 200 mm.

  The end on the front or back surface of the block-shaped foamed molded product in the mold according to the present invention refers to the vicinity of the mold end surface on the front or back surface, and the length of the end is 1 to 20 of the length or width of the mold cavity. %, More preferably 5 to 10%. When the length of the end portion is too large, it is difficult for steam and cooling water to flow, and the fusion property between the expanded particles at the end portion of the foamed molded product tends to decrease. On the other hand, if the length of the end portion is too small, deformation and shrinkage occur at the end portion of the foamed molded product, and the dimensional stability tends to be lowered. The length of the end depends on the size of the mold, but is usually preferably 10 mm or more and 100 mm or less from the end face of the mold. Here, the mold end surface refers to four surfaces corresponding to the upper and lower surfaces and the left and right side surfaces of the block-shaped foamed molded body among the six surfaces of the mold constituting the mold cavity.

  The mold of the present invention is a mold using polyolefin resin expanded particles. Compared with polystyrene resin foam particles, polyolefin resin foam particles require high-pressure steam (high temperature steam) to fuse the foam particles. For this reason, in molding using polyolefin resin expanded particles, if a mold with a large opening ratio is used, it is considered that excessive steam flows near the end of the mold, and deformation and shrinkage of this part are likely to occur. The It is considered that when the opening ratio of the end portion is reduced as in the mold of the present invention, deformation and contraction of the end portion can be prevented.

  The polyolefin resin expanded particles used in the present invention are produced from a polyolefin resin. Examples of such polyolefin resins include polypropylene resins, polyethylene resins, styrene-modified polyolefin resins, and the like.

  Examples of the polypropylene resin include a propylene homopolymer, a propylene-α-olefin random copolymer, and a propylene-α-olefin block copolymer. Examples of the α-olefin herein include α-olefins having 2 to 4 to 15 carbon atoms, and these may be used alone or in combination of two or more. Among these polypropylene resins, propylene-ethylene random copolymer, propylene-ethylene-butene-1 random copolymer, propylene-butene-1 random copolymer, and a comonomer content other than propylene is 1 to 5 wt. % Polypropylene-based resin exhibits good foaming properties and can be suitably used. In addition, the copolymer polymer is suitable because it has a characteristic that a foaming agent such as carbon dioxide is easily impregnated as compared with a homopolymer.

  When a polypropylene resin is used, the melting point is preferably 130 ° C. or higher and 165 ° C. or lower, and more preferably 135 ° C. or higher and 155 ° C. or lower. It is preferable because expanded particles having excellent mechanical strength and heat resistance can be obtained. Here, the melting point is that the sample 1 to 10 mg is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter, then cooled to 40 ° C. at a rate of 10 ° C./min, and again 220 The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is raised to 10 ° C. at a rate of 10 ° C./min.

  Furthermore, the melt index (MI) of the polypropylene resin is preferably 2 g / 10 min or more and 11 g / 10 min or less, more preferably 3 g / 10 min or more and 10 g / 10 min or less, and most preferably 4 g / 10 min or more. It is 8 g / 10 minutes or less. When the melt index is less than 2 g / 10 minutes, it becomes difficult to obtain expanded particles having a high expansion ratio, and the bubbles tend to be non-uniform. In addition, when the melt index exceeds 11 g / 10 min, it is easy to foam, and it is easy to obtain expanded particles with a high expansion ratio, but the expanded cells tend to break, and the open cell rate of the expanded particles tends to increase. , Bubbles also tend to be non-uniform. The melt index of the polypropylene resin is a value measured at a temperature of 230 ° C. and a load of 2.16 kg in accordance with JIS K7210.

  Examples of the polyethylene resin include ethylene homopolymer, ethylene-α-olefin random copolymer, ethylene-α-olefin block copolymer, low density polyethylene, high density polyethylene, and linear low density polyethylene. The α-olefin referred to herein includes α-olefins having 3 to 15 carbon atoms, and these may be used alone or in combination of two or more. Among these polyethylene-based resins, good foamability when ethylene-α-olefin block copolymer has a comonomer content other than ethylene of 1 to 10% by weight or is a linear low density polyethylene And can be suitably used.

  When a polyethylene resin is used, the melting point is preferably 110 ° C. or higher and 140 ° C. or lower, and further 120 ° C. or higher and 130 ° C. or lower is excellent in foamability and moldability, and is made into a block-like foam molded article. It is preferable because expanded particles having excellent mechanical strength and heat resistance can be obtained. Further, the melt index (MI) of the polyethylene resin is preferably 0.5 g / 10 min or more and 30 g / 10 min or less, more preferably 1 g / 10 min or more and 5 g / 10 min or less, most preferably It is 1.5 g / 10 min or more and 2.5 g / 10 min or less. When the melt index is less than 0.5 g / 10 min, it becomes difficult to obtain expanded particles with a high expansion ratio, and the bubbles tend to be non-uniform. In addition, when the melt index exceeds 30 g / 10 min, foaming tends to occur, but the foamed cells tend to break, the foaming rate of the foamed particles tends to increase, and the bubbles tend to be non-uniform. . The melt index of the polyethylene resin is a value measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210.

  In the present invention, the catalyst used for producing the polyolefin resin is not particularly limited, and examples thereof include a Ziegler-Natta catalyst and a metallocene catalyst. These polyolefin resins may be used alone or in combination of two or more. Since the effects of the present invention are more remarkably exhibited, it is preferable to use a polypropylene resin as the polyolefin resin.

  Polyolefin resin is usually melted in advance using an extruder, kneader, Banbury mixer, roll, etc. so as to be easily used for pre-foaming, and is desired to have a cylindrical shape, elliptical shape, spherical shape, cubic shape, rectangular parallelepiped shape, etc. The particle shape is formed. The average particle weight of the polyolefin resin particles is preferably 0.5 mg to 3.0 mg, particularly preferably 0.5 mg to 2.0 mg, and more preferably 0.5 mg to 1.5 mg.

  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 foamed 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.

  When producing polyolefin resin particles, if necessary, colorants, antistatic agents, antioxidants, phosphorus processing stabilizers, lactone processing stabilizers, metal deactivators, benzotriazole UV absorbers, benzoate light stabilizers Additives such as additives, hindered amine light stabilizers, flame retardants, flame retardant aids, acid neutralizers, crystal nucleating agents and amide additives may be added within a range that does not impair the properties of the polyolefin resin. it can.

  The polyolefin resin particles can be made into polyolefin resin foamed particles using a conventionally known method. For example, the polyolefin resin particles are dispersed in a dispersion medium such as water in a pressure vessel, and after adding a foaming agent, the polyolefin resin particles are heated to a temperature higher than the temperature at which the polyolefin resin particles soften and pressurized. After impregnating the foaming agent, one end of the pressure vessel is opened, and the polyolefin resin particles are produced by releasing the polyolefin resin particles into a lower pressure atmosphere than the pressure vessel.

  In order to prevent coalescence of the polyolefin resin particles in the dispersion medium, it is preferable to use a dispersant. Examples of the dispersant include inorganic dispersants such as tricalcium phosphate, tribasic magnesium phosphate, basic magnesium carbonate, calcium carbonate, barium sulfate, kaolin, talc, and clay.

  There are no particular limitations on the type of blowing agent, for example, aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane; inorganic gases such as air, nitrogen, and carbon dioxide; water and the like, and mixtures thereof Can do.

  In the case of a styrene-modified polyolefin-based resin, for example, foamed particles can be obtained by the method described in JP-A-2005-97555.

  When the obtained polyolefin resin expanded particles are subjected to in-mold foam molding using the mold of the present invention, a) a method in which the obtained polyolefin resin expanded particles are used as they are; b) air or the like in the expanded particles in advance. Conventionally known methods such as a method of press-fitting the inorganic gas and imparting foaming ability, c) a method of filling foamed particles into a mold in a compressed state, and the like can be used. Among them, a method of imparting foaming ability by press-fitting an inorganic gas such as air into the foamed particles in advance is preferable. Specifically, the polyolefin resin expanded particles are preliminarily air-pressurized in a pressure resistant container, and the foaming ability is imparted by press-fitting air into the polyolefin resin expanded particles.

  Next, the manufacturing method of the block-shaped foaming molding which uses the metal mold | die of this invention, fills a mold cavity with polyolefin-type resin foaming particles, and performs foam molding in a mold | die is demonstrated using FIG. The movable mold 1b is moved to a predetermined position to form the mold cavity 12, and the pressurized air introduced from the air introduction port 17 of the feeder 15 is used to introduce the foam particles introduced from the foam particle introduction port 16 into the mold cavity 12. Fill. At this time, the air is discharged from the drain valves 11a and 11b through the gaps and slits of the plurality of rod-shaped members.

  In order to make the air in the mold cavity 12 easy to escape, the movable mold may be opened a little and filled with a gap 20 formed between the fixed mold 1a and the movable mold 1b (cracking filling). In this case, air is discharged not only from the drain valves 11a and 11b but also from the gap 20 between the fixed mold and the movable mold via the gap 19 between the middle mold 4a and the middle mold 4b.

  After filling the expanded particles, the feeder is closed by the piston 18, and in the case of cracking filling, the movable mold 1b is moved to a predetermined position, the mold is closed, and the process proceeds to the heating step. First, while supplying steam from the steam valve 10a and the steam valve 10b to the steam chambers 9a and 9b with the fixed drain valve 11a and the movable drain valve 11b being opened, the air in the two steam chambers is used as a system. Drain outside (preheating process). Next, by supplying steam to one steam chamber and exhausting it from the other steam chamber, the air in the mold cavity is discharged out of the system, and the polyolefin resin foam particles and the middle mold 4a and the middle mold 4b are preheated. (One heating process, reverse one heating process). Next, with the two drain valves 11a and 11b closed, steam is supplied to the two steam chambers to heat the polyolefin-based resin foam particles (double-sided heating step). The heating temperature varies depending on the resin type and expansion ratio, but is set to 0.09 MPa (G) to 0.12 MPa (G) for polyethylene resins and 0.25 MPa (G) to 0.45 MPa (G) for polypropylene resins. It is preferable to do.

  When the heating is completed, the process proceeds to the cooling process. In the cooling process, cooling water is sprayed from a nozzle unit (not shown) generally provided in the steam chambers 9a and 9b toward the middle mold 4a and the middle mold 4b, and inside the mold cavity 12 through these middle molds. This is a step of cooling and solidifying the foamed molded product to a releasable hardness. The cooling process is divided into a cooling process initial stage (pre-cooling process) and a cooling process late stage (water cooling process).

  After the heating process is completed, at the initial stage of the cooling process, cooling water is introduced into the mold with the two drain valves 11a and 11b closed, and the pressure in the mold is reduced to atmospheric pressure. When the pressure in the mold is reduced, the two drain valves are opened, and the process proceeds to the latter stage of the cooling process. In the latter stage of the cooling process, the foam molded body in the mold cavity 12 is cooled and solidified to the hardness of the foam molded body that can be released. Thereafter, the movable mold 1b is opened and the foamed molded article is taken out using an unillustrated extrusion pin or the like to obtain a block-shaped foam molded article.

  The block-shaped foamed molded product of the present invention obtained as described above has a convex portion that is a vapor hole trace on the upper surface, the lower surface, and the left and right side surfaces of the block-shaped foamed molded product in a range of 0.5% to 5%. It is preferable that the convex portion which is a vapor hole trace on the inner side of at least one of the two surfaces corresponding to the front surface and the back surface of the block-shaped foamed molded body is 7% to 30%.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

Example 1
Polypropylene with MI: 7 g / 10 min, melting point: 141 ° C., ethylene content: 4 wt% was used as the base resin, and after adding a cell nucleating agent and melt-kneading in an extruder, it was made into a strand from a circular die. Extrusion, water cooling, and cutting with a cutter were performed to obtain 1.8 mg / grain weight of the resin particles having a cylindrical shape. 100 parts by weight (65 kg) of the obtained resin particles, 200 parts by weight of water, 0.5 parts by weight of basic tricalcium phosphate and 0.01 parts by weight of sodium alkyl sulfonate are charged into a pressure-resistant autoclave, and as a foaming agent under stirring. After adding 16 parts by weight of isobutane, the autoclave contents were heated to a foaming temperature of 135 ° C. Thereafter, isobutane was additionally injected, the valve at the bottom of the autoclave was opened, and the contents were released under atmospheric pressure to obtain expanded particles. Air was press-fitted into the expanded polypropylene resin particles by air pressure treatment to obtain expanded polypropylene resin particles to which an internal pressure was applied.

  In-mold foam molding was performed using a block-shaped mold shown in FIG. 1 having a mold cavity size of 900 × 900 × 50 mm. However, in the movable vertical member, the core vent was used for the length portion of 50 mm from the end portion, and the opening ratio was 1.5%. In the movable vertical member, a member in which a plurality of rod-shaped members having a triangular cross section are arranged in parallel on the inner side from the end portion is used, and the aperture ratio is set to 14.3%.

  With the mold closed, the polypropylene resin expanded particles to which the internal pressure was applied were filled into the mold. Heating is performed in the exhaust process for 5 seconds (with the drain valves on the fixed mold side and movable mold side opened), one heating for 10 seconds, reverse one heating for 5 seconds, double-sided heating for 20 seconds (vapor pressure 0.11 MPa (G)) After completing the heating step, pre-cooling for 5 seconds (cooling with the drain valve closed) and water-cooling for 30 seconds, the block-shaped foamed molded product is released, and the particles are fused well at the end. A good block-like foamed molded article free from shrinkage and deformation was obtained.

(Comparative Example 1)
Instead of the two medium molds used in the first embodiment, two medium molds having an aperture ratio of 14.3% using a member in which a plurality of rod-shaped members having a triangular cross-section are arranged in parallel are used. In-mold molding was performed in the same manner as in Example 1. The obtained block-shaped foamed molded article had good fusion between the particles, but it became a block-shaped foamed molded article that was partially contracted and deformed at the end.

DESCRIPTION OF SYMBOLS 1a Fixed type 1b Movable type 2a, 2b Frame 3a, 3b Center plate 4a, 4b Middle type 5a, 5b Upper member 5a ', 5b' Lower member 6a, 6b Vertical member 7b End part 8b Inner part 9a, 9b Steam chamber 10a, 10b Steam valve 11a, 11b Drain valve 12 Mold cavity 13 Slit formed at the end 14 Gap between a plurality of rod-shaped members 15 Feeder 16 Foamed resin particle inlet 17 Air inlet 18 Piston 19 Gap between the middle die 4a and the middle die 4b 20 Clearance between fixed mold 1a and movable mold 1b

Claims (5)

In a mold for filling a polyolefin resin expanded particle into a mold cavity and foaming and fusing the polyolefin resin expanded particle with steam to produce a block-shaped foamed molded article, Among them, the opening ratio of the vapor holes in the four mold surfaces corresponding to the upper surface, the lower surface, and the left and right side surfaces of the block-shaped foamed molded product is 0.5% or more and 5% or less. In at least one of the two corresponding mold surfaces, the opening ratio of the steam holes at the end is 0.5% or more and 5% or less, and the opening ratio of the steam holes at the inner part is 7% or more and 30% or less. , and the and the mold surface of the inner portion using a plurality of rod-shaped member via a predetermined gap is composed of a member arranged in parallel lube lock-shaped molded foam product manufacturing mold, polyolefin type fossa In-mold foaming Process for producing a polyolefin resin block foamed molded article, characterized by. The end of at least one of the two mold surfaces corresponding to the front and back surfaces of the block-shaped foamed molded body in the mold is within 100 mm from the mold end surface. The manufacturing method of the polyolefin-type resin block-shaped foaming molding of description . In the member in which the plurality of rod-shaped members are arranged in parallel through a certain gap, the width of the plurality of rod-shaped members is set to 2 mm or more and 4 mm or less, and the gap for arranging these rod-shaped members is set to 0.25 mm or more and 0.75 mm or less. The method for producing a polyolefin resin block-like foam molded article according to claim 1 or 2 . Polyolefin resin block foamed molding according to claims 1 to 3 any one, characterized in that members which arranged the plurality of bar-like members in parallel through a fixed gap is produced of stainless Production method. In a mold for filling a polyolefin resin expanded particle into a mold cavity and foaming and fusing the polyolefin resin expanded particle with steam to produce a block-shaped foamed molded article, Among them, the opening ratio of the vapor holes in the four mold surfaces corresponding to the upper surface, the lower surface, and the left and right side surfaces of the block-shaped foamed molded product is 0.5% or more and 5% or less. In at least one of the two corresponding mold surfaces, the opening ratio of the steam holes at the end is 0.5% or more and 5% or less, and the opening ratio of the steam holes at the inner part is 7% or more and 30% or less. , and the and the block-like foam molding mold surface of the inner portion are obtained using configured block-shaped molded foam product manufacturing mold of a member arranged a plurality of bar-like members in parallel through a fixed gap Body, block-like foam molding The convex part which is the vapor hole trace of the upper surface, the lower surface, and the left and right side surfaces is 0.5% or more and 5% or less, and the inner part of at least one of the two surfaces corresponding to the front surface and the back surface of the block-shaped foam molded body The polyolefin resin block-like foamed molded article is characterized in that the convex portions, which are the traces of vapor holes, are 7% or more and 30% or less.

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