JPH0461766B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is made of polypropylene, which has an expansion ratio of 2.5 times or less, has a uniform foam layer with fine foam cells, and has both or one side of the foam layer covered with a non-foam layer made of polypropylene. This invention relates to multilayer sheets. Generally, multilayer sheets made by laminating two or more types of plastics are used as sheet materials that have various properties such as heat resistance, abrasion resistance, chemical resistance, and aging resistance. One layer of this multilayer sheet is often a foamed multilayer sheet material with at least a foam layer, and these foamed multilayer sheets exhibit various properties of the foam layer such as lightness, heat insulation, and cushioning properties, In order to compensate for the decrease in strength caused by foaming, it is used as an excellent structural material that maintains mechanical strength by laminating non-foamed layers. More specifically, by taking advantage of the properties of polypropylene sheets such as impact resistance, heat resistance, chemical resistance, and aging resistance, they can be used as automobile interior materials or home appliance parts materials, as well as their light weight and heat insulation properties. It is widely applied. For these uses, it is necessary to maintain the rigidity and heat resistance of the foam layer as much as possible, and in the present invention, fillers are added to polypropylene to increase rigidity and heat resistance.
It was essential to increase heat resistance. These multilayer sheets are manufactured by, for example, the method exemplified in JP-A-50-55683. Normally, when manufacturing a multilayer sheet having a foam layer made of polypropylene with a relatively low magnification, the foam layer is formed by adding a predetermined amount of a pyrolyzable chemical foaming agent to polypropylene in advance, and heating and melting the polypropylene. However, the foam layer is usually made from polypropylene pellets containing a filler with finely granulated foaming agents added, so they are easy to classify during the feeding process from the hopper to the cylinder.
Dispersion of the blowing agent in the molten plasticized product becomes uneven,
As a result, foaming is non-uniform and a homogeneous molded product cannot be obtained. In the multilayer sheet of the present invention, the key point is uniform foaming of the foam layer, and if the foam layer is uneven, when covering both sides or one side of the foam layer with a non-foam layer, it is necessary to create a smooth multilayer sheet with commercial value. The reality is that sheet manufacturing is difficult. As a result of intensive studies, the present inventors found that a homogeneous mixture of granular polypropylene for molding and a foaming agent, in which a filler is attached to the surface of granular polypropylene using a binder, or a foaming agent and a filler bonded to the surface of granular polypropylene, When granular polypropylene for foam molding attached with a foaming agent is used as a raw material for forming a foam layer in a multilayer sheet, the foam layer foams uniformly, and the surface covered with the non-foam layer is smooth and has sufficient commercial value. I found it. That is, the present invention relates to a polypropylene multilayer sheet having an expansion ratio of 2.5 times or less, having a foam layer with fine foam cells and a uniform foam layer, and having both or one side of the foam layer covered with a non-foam layer made of polypropylene. In addition, the raw materials for forming the foam layer include granular polypropylene for molding having at least one layer consisting of a filler and a binder on the surface of granular polypropylene with a bulk specific gravity of 0.45 or more and an average particle size of 150 to 2000 microns, and a foaming agent. granular polypropylene for foam molding having at least one layer consisting of a filler, a binder, and a blowing agent on the surface of the granular polypropylene. The present invention will be explained in detail below. The granular polypropylene for molding and the granular polypropylene for foam molding used as raw materials for forming the foam layer in the present invention are disclosed in JP-A-57-74338;
It is manufactured based on the method described in Japanese Patent Application No. 175487/1987 previously filed by the present inventors. The granular polypropylene used in the present invention includes propylene homopolymers, random copolymers and block copolymers of propylene and other α-olefins, and preferably these polyolefins are crystalline. It has a bulk specific gravity of 0.45 or more and an average particle size of 150 to 2000 microns. If the bulk specific gravity is less than 0.45, it is not preferable because there are many voids inside the particles and between the particles and sufficient deaeration cannot be carried out during molding. If the particle size is too small, it is not preferable because it tends to scatter, and especially if it is less than 100 microns, it is likely to cause a dust explosion.
On the other hand, if the particle size is too large, the dispersion of the blowing agent and filler in the resulting molded product will be poor. Furthermore, the closer the shape of the granular polypropylene is to a spherical shape and the narrower the particle size distribution, the more preferable it is. The shape is basically determined by the polymerization catalyst used during its production. As an example of producing polypropylene with preferable properties suitable for the present invention, a titanium trichloride composition obtained by reducing titanium tetrachloride with an organoaluminum compound and further activating the polymer is shown. propylene or propylene and other olefins in an inert solvent, or in an excess of liquid propylene in the substantial absence of an inert solvent, using a catalyst system consisting of an organoaluminum compound and optionally an electron-donating compound, or in a gas phase. It can be obtained by polymerization in the same conditions. A specific example of the method for producing a titanium trichloride composition is given in Japanese Patent Application Laid-Open No. 1987-
This method has been proposed in JP-A No. 34478, Japanese Patent Application Laid-open No. 76196-1987, and so on. The filler used in the present invention is one that has been added to improve the physical properties of polypropylene, and specific examples include silica, diatomaceous earth, alumina, titanium oxide,
iron oxide, zinc oxide, magnesium oxide, pumice powder,
Examples include aluminum hydroxide, magnesium hydroxide, potassium carbonate, magnesium carbonate, potassium sulfate, barium sulfate, talc, clay, mica, glass beads, carbon black, and mixtures of two or more thereof. The size of the inorganic filler is not particularly limited, but is usually 50 microns or less, preferably 30 microns or less, and it is preferable to use a finer filler as the particle size of the core granular polyolefin becomes smaller. The amount of filler is generally in the range of 0.1 to 150 parts by weight, preferably 10 to 150 parts by weight, based on 100 parts by weight of granular polypropylene. The binder of the present invention has the role of firmly adhering the inorganic filler and/or foaming agent to the surface of the granular polypropylene, and for this purpose, it must be in a molten state at a temperature at least 3° C. lower than the melting point of the granular polypropylene. In view of the quality of the molded product, it is preferable to use a material that has good compatibility with granular polypropylene. Examples of binders include polyethylene, ethylene-vinyl acetate copolymers, ethylenically unsaturated carboxylic acid ester copolymers (e.g. ethylene-methyl methacrylate copolymers, etc.), and ethylene-unsaturated carboxylic acid metal salt copolymers ( For example, ethylene-magnesium acrylate or zinc copolymer),
Propylene and other olefin copolymers (propylene-ethylene copolymer, propylene-butene-1
copolymers, etc.), polyethylene or polypropylene modified with unsaturated carboxylic acids such as maleic anhydride, olefins such as ethylene-propylene rubber, ethylene-butene-1 rubber, and atactic polypropylene, copolymers, petroleum resins, polyethylene Examples include polyalkylene glycols such as glycol and polypropylene glycol. In particular, polyethylene, ethylene-vinyl acetate copolymers, ethylene-unsaturated carboxylic acid ester copolymers (e.g. ethylene-methyl methacrylate copolymers, etc.), ethylene-unsaturated carboxylic acid metal salt copolymers (e.g. ethylene-acrylic copolymers of propylene and other olefins (propylene-ethylene copolymers,
propylene-butene-1 copolymers, etc.), polyethylene or polypropylene modified with unsaturated carboxylic acids such as maleic anhydride, ethylene-propylene rubber, ethylene-butene-1 rubber, atactic polypropylene and other olefin copolymers. preferable. Generally, molded articles made of polypropylene to which an inorganic filler is added have higher rigidity than molded articles without additives, but have lower impact resistance. On the other hand, it is preferable to use an olefin copolymer as the binder in the granular polypropylene material for molding of the present invention because the impact strength is less reduced or the strength is improved. For example, when using granular polypropylene,
It is preferable to use polyethylene, propylene-butene-1 copolymer, ethylene-propylene rubber, ethylene-butene-1 rubber, or atactic polypropylene as the binder because impact strength is improved. These binders may be used alone or in combination. The amount of binder varies depending on the type and amount of the inorganic filler and blowing agent, so it can be determined appropriately taking these into consideration, but usually the weight ratio of binder/(inorganic filler + blowing agent) is about 1/ 10 to about 1/2, preferably about 1/10 to about 1/4. The blowing agent in the present invention is a compound that is fixed at room temperature and generates gases such as nitrogen, carbon dioxide, and ammonia gas when heated above the decomposition temperature. or have a decomposition temperature at least 5°C higher than the pour point, such as dinitrosopentamethylenetetramine, azodicarbonamide, metal salts of azodicarbonamide, 4,4'-oxybis(benzenesulfonyl hydrazide), toluenesulfonyl hydrazide. Known organic or inorganic blowing agents such as sodium bicarbonate, ammonium carbonate, etc. are used. In addition, these blowing agents may be used alone or in combination of two or more, and may be used in combination with known blowing aids such as urea, urea-based compounds, zinc white, and zinc stearate. Good too. The amount of blowing agent used is usually based on 100 parts by weight of resin and filler.
0.1 to 10 parts by weight, depending on the desired foaming ratio,
It may be changed as appropriate depending on the molding method, the type of blowing agent used, and the amount of gas generated. If the amount of blowing agent used is less than the above lower limit, the expansion ratio will be too low, and if it is more than the above upper limit, the amount of gas generated by the decomposition of the blowing agent will be too large, which will not be able to withstand the viscosity of the resin, resulting in cracks in the foam. The gas escapes to the outside, causing contraction, and making it difficult to maintain a uniform thickness of the foam layer.
As a result, a smooth sheet cannot be obtained even if the non-foamed layer is coated. From the above point, it is necessary that the foaming ratio be 2.5 times or less. Further, as the material for forming the non-foamed layer made of polypropylene with a diameter of 500 microns or less, a polypropylene homopolymer or a copolymer consisting of one or more α-olefins other than propylene and propylene can be used. Furthermore, in order to improve the physical properties of the granular polypropylene material for foam molding of the present invention, various antioxidants, light stabilizers and pigments that are conventionally added to improve the stability and quality of polypropylene may be used. The amount of these compounds may be appropriately determined in consideration of the amount of adhesion, but since the amount added is generally smaller than that of the filler, there is no problem even if the amount of the binder is greater than the amount of the compounding agent. Examples of stabilizers include antioxidants such as 2,6-ditertyabutyl para-cresol, calcium stearate, and tetra[methylene-3-
(3,5 ditertiarybutyl-4-hydroxyphenyl) propionate] methane, etc.; light stabilizers such as 2-(2'-hydroxy-5'-methylphenyl) benzotriazole, 2-hydroxy-4-
Examples include, but are not limited to, octylbenzophenone. Examples of pigments include organic or inorganic pigments used for coloring polypropylene. An example of the method for producing the granular polypropylene material for foam molding of the present invention will be shown below. The equipment used is a mixer equipped with an agitator that can heat the contents, such as a Henschel mixer,
Examples include Super Mixer (trade name, manufactured by Kawada Seisakusho Co., Ltd.). In this mixer, the granular polyolefin, inorganic filler, binder, and/or foaming agent are mixed, as necessary, and various other ingredients are heated to a temperature slightly higher than the melting point of the binder. As a result, the molten binder, including the inorganic filler, various compounding agents, and/or blowing agent, firmly and uniformly adheres to the surface of the granular polypropylene. If this is taken out as it is or after being slightly cooled, polypropylene for forming grains with good fluidity can be obtained. When produced in this manner, the binder preferably remains molten at a temperature at least 3° C. below the melting point of the particulate polypropylene and at least 5° C. below the decomposition temperature of the blowing agent. This is to prevent the granular polypropylene from melting and to prevent the blowing agent from decomposing in the mixer. Further, the shape of the binder is preferably as small as possible in order to improve the dispersion of the filler and foaming agent and to melt the binder in a short time. For example, if polyethylene is used as a binder, it is better to crush the pellets and use a powder that has passed through 30 meshes than to use the pellets obtained by extrusion granulation as is because the filler and blowing agent will be more uniformly dispersed. Can be attached in a short time. Next, the multilayer sheet manufacturing apparatus is not particularly limited, but by way of example, the following apparatus can be used to obtain the desired multilayer sheet. In other words, by using a flat die that has a plurality of manifolds and resin passages connected to a plurality of extruders and a merging resin passage in which flows from the plurality of resin passages merge and become one, the foam layer material and the non-containing resin are separated in the die. The foam layer material is fused into a single piece in a confluent resin passage and extruded to form a multilayer sheet. Next, the present invention will be specifically explained with reference to the illustrated embodiments. In FIG. 1, the foam layer material forming the inner layer sent out from the main extruder (not shown) is in the die body 1.
The resin is distributed over the entire width of the die by an inner layer manifold 2 provided inside the die, is adjusted to a uniform flow rate by an inner layer choke bar 13, passes through a resin passage 9 formed by inner layer lips 5 and 6, and flows into a confluent resin formed by die lips 7 and 8. You will be led to passage 12. The non-foamed layer material forming the surface layer sent out from the sub-extruder (not shown) is distributed over the entire width of the die by the surface layer manifolds 3 and 4, and then passed through the surface layer manifolds 3 and 4 to the surface layer manifolds 3 and 4.
The flow rate is adjusted to be uniform by the resin passages 10, 1.
1 and is led to a confluent resin passage 12. The inner layer and the surface layer are fused and integrated into a single resin in the merged resin passage 12 formed by the die lips 7 and 8, and the resin is extruded from the die outlet. FIG. 2 shows an example of the cross section of the polypropylene multilayer sheet extruded in this manner. 16 and 18 are non-foamed layers made of polypropylene, and 17 is a foamed layer. FIG. 3 shows a polypropylene multilayer sheet with a non-foamed layer formed on only one side. 19 is a non-foamed layer made of polypropylene, and 20 is a foamed layer. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited thereto. Example 1 (1) Polymerization of propylene A stirred stainless steel autoclave with an internal volume of 300 was purged with nitrogen, and 1800 g of diethylaluminum chloride was prepared as shown in Example 15 and Catalyst Preparation Method 3 of JP-A-53-33289. Charge 50 g of titanium trichloride solid catalyst (B) obtained by the method,
Hydrogen was added corresponding to a partial pressure of 0.5 Kg/cm ² . Then, 840 kg of liquid propylene was pressurized into the autoclave, and the autoclave was kept at 65°C to continue polymerization for 4 hours. After the polymerization was completed, unreacted monomers were purged and methanol 60% was added to decompose the catalyst. The produced polypropylene was separated using a centrifuge and dried under reduced pressure at 60°C, yielding spherical granular polypropylene with a uniform particle size of 390 kg. The melting point of this polypropylene was measured using a differential thermal calorimeter (manufactured by PerkinElmer).
When measured, it was 165℃. The average particle size of this granular polypropylene was about 600 microns, and the bulk specific gravity was about 0.49. (2) Production of foam molding material (A) Steam of 2 kg/cm ² G was passed through a 100 Super Mixer (trade name, manufactured by Kawada Seisakusho Co., Ltd.). to this
(1) 17.5 kg of granular polypropylene obtained by polymerization of propylene, Sumikasen G801 as a binder (low-density polyethylene melting point 110°C, manufactured by Sumitomo Chemical Co., Ltd.)
0.5 kg of powder passed through 30 meshes, Cellmic CAP (decomposition temperature 125°C, manufactured by Sankyo Kasei Co., Ltd.) 0.4 as a foaming agent
Kg, 2.0Kg of talc with an average particle size of 8 microns as an inorganic filler and tertiary butyl p as a stabilizer.
-cresol/tetra[methylene-3-(3,5
- diterciabutyl-4-hydroxyphenyl)propionate] methane = 2/1) weight ratio}
80g was added and stirred at 675rpm. 12 after starting stirring
The temperature reached 115℃ in minutes, so I released the contents.
A spherical, smooth molding material was obtained. The foaming agent, talc, and stabilizer adhered uniformly and firmly to the granular polypropylene, and no peeling of the foaming agent, talc, and stabilizer was observed even when the product was placed in the palm of the hand and rubbed strongly with the fingertips. Almost no adhesion was observed on the inner wall of the super mixer. (3) Molding of multilayer sheet The above-mentioned foam molding material (A) was used as the foam layer material, and polypropylene (Sumitomo Noblen FL6411MI=7, manufactured by Sumitomo Chemical Co., Ltd.) was used as the non-foam layer material. Using the apparatus shown, multilayer sheets having the configurations shown in Table 1 were obtained at molding temperatures of an extruder temperature of 220°C and a soybean temperature of 200°C in each case. The multilayer sheet of the present invention includes a sheet having a foam layer with an expansion ratio of 3.0 times, and a polypropylene pellet containing a filler (Noblen BWH52/
The surface covered with the non-foamed layer is smoother and smoother than a sheet made using a dry blend of the same amount of foaming agent (Celmic CAD) (1:1 blend of W501) (foam molding material B). It had commercial value. 【table】

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a die used to extrude the multilayer sheet of the present invention. Figure 2 shows
FIG. 2 is a cross-sectional view of a multilayer sheet obtained using the die of FIG. 1; FIG. 3 is a sectional view of another example of the multilayer sheet of the present invention. In the figure, 1 is the die body, 2 is the inner layer manifold, 3, 4 are the surface layer manifolds, 5, 6 are the inner layer lips, 7, 8 are the die lips, 9, 10, 11,
12 is a resin passage, 13 is an inner layer choke bar, 1
4, 15 are surface layer chiyoke bars, 16, 18, 19
1 shows a polypropylene non-foamed layer, and 17 and 20 show a foamed layer, respectively.

Claims (1)

[Scope of Claims] 1. Granular polypropylene for molding having at least one layer consisting of a filler and a binder on the surface of granular polypropylene having a bulk specific gravity of 0.45 or more and an average particle size of 150 to 2000 microns, and a foaming agent, or bulk specific gravity is 0.45
As mentioned above, it has a foam layer obtained by heating and extruding granular polypropylene for foam molding, which has at least one layer consisting of a filler, a binder, and a foaming agent on the surface of granular polypropylene with an average particle size of 150 to 2000 microns. A polypropylene multilayer sheet, wherein both or one side of the foamed layer is coated with a non-foamed polypropylene layer. 2. A patent claim in which the binder is an olefinic polymer in a molten state at a temperature at least 3°C lower than the melting point of the granular polypropylene, and the blowing agent has a decomposition temperature at least 5°C higher than the melting point or pour point of the binder. A polypropylene multilayer sheet according to item 1. 3. The polypropylene multilayer sheet according to claim 1, which has a foam layer having an expansion ratio of 2.5 times or less. 4. The polypropylene multilayer sheet according to claim 1, wherein both or one side of the foam layer is coated with a non-foamed polypropylene layer having a thickness of 500 microns or less.