JP2004346180A - Process for producing styrenic resin foam and styrenic resin foam board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a styrenic resin foam which has fine cells by uniform expansion at a high expansion ratio, smooth and good surface appearance, can be uniformly printed beautifully without causing a white void when directly printed on its surface by a roll, shows a beautiful cut surface without causing feathering when cut by a guillotine or a slicing machine, and is easy in post-processing. <P>SOLUTION: The process for producing the styrenic resin foam comprises extrusion foaming with the use of an ethylene tetrafluoride resin powder and a talc powder as foam conditioners at a specific ratio. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【図面の簡単な説明】
【図１】実施例１で用いた四弗化エチレン樹脂の微粉末の走査型電子顕微鏡写真である。この写真から一次粒子がブドー状に集合し、塊状体を形成している事がわかる。
【図２】一次粒子の粒径が１５μｍの四弗化エチレン樹脂の微粉末の走査型電子顕微鏡写真である。
【図３】実施例１で得られた発泡体の断面の走査型電子顕微鏡写真である。この写真から発泡体の厚み方向の気泡構造において表面層の気泡径が特に細かくなっており、融着界面層の気泡径は微細になっていないことがわかる。
【図４】比較例２で得られた発泡体の断面の走査型電子顕微鏡写真である。この写真から発泡体の厚み方向の気泡構造おいて、表面層と融着界面層の気泡径が特に細かくなっていることがわかる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a styrene resin foam. In particular, the present invention is not only a foam having a uniform appearance with high magnification and having fine air bubbles, a smooth surface and a good appearance, but also easy to be post-processed such as cutting or printing, and providing a beautiful finish. And a method for producing a styrene resin foam. The present invention also relates to a styrene-based resin foam plate thus obtained.
[0002]
[Prior art]
Styrene-based resin is a resin that is easily foamed among synthetic resins. Accordingly, there are various methods for producing a styrene resin foam. One of them is an extrusion foaming method. With the extrusion foaming method, a styrene-based resin is put into an extruder, the resin is melted in the extruder, a foaming agent is included in the molten resin, and the foaming agent-containing molten resin is extruded from the extruder to a low-pressure region and extruded. At the same time, the resin is foamed to form a foam.
[0003]
According to the extrusion foaming method, since a foam having a uniform cross section can be continuously produced, the foam can be efficiently produced. For this reason, sheets, plates, and the like, which are made of a styrene-based resin, are produced exclusively by an extrusion foaming method.
[0004]
In order to produce a styrene-based resin foam plate that is uniformly and finely foamed by the extrusion foaming method, an air conditioner is used in addition to the foaming agent. Cell regulators are also called foam nucleating agents or simply nucleating agents. The foam control agent is to be the core of the foam at the time of foaming, and is considered to be very important. This is because it is considered to determine the number of cells generated in the foam, the size of the cells, and the shape of the cells.
[0005]
Various foam control agents have been used so far. Many of them are inorganic powders. For example, calcium carbonate, talc, calcium silicate, diatomaceous earth, barium sulfate and the like have been used. In addition to inorganic substances, organic substance powders such as magnesium stearate and ethylene tetrafluoride resin are also used as air bubble regulators. In particular, talc is generally and preferably used.
[0006]
Japanese Patent Application Laid-Open No. 7-138403 proposes to use a specific tetrafluoroethylene resin as a cell regulator when foaming a thermoplastic resin in addition to a styrene-based resin to form a foam. ing. The specific ethylene tetrafluoride resin is a resin that exhibits a specific melt viscosity when the ethylene tetrafluoride resin is melted under high temperature and high pressure.
[0007]
Including the case of using the above-mentioned tetrafluoroethylene resin, styrene-based resin foams made by adding various cell regulators to styrene-based resin and extruding the styrene-based resin are foamed uniformly and finely. It has a smooth surface and is a good foam board. However, the conventional foamed board could not satisfy the requirements of the market when performing the processing described below.
[0008]
Styrene-based resin foam boards have recently been directly printed thereon and used as decorative or display materials. The printing is performed using a roll. At this time, the styrene-based resin foam plate obtained by the conventional extrusion foaming has been difficult to print uniformly because of overexposure and color unevenness in some places. In other words, the conventional styrene-based resin foam plate has a smooth surface, but in fact, small valleys are formed between the bubbles, which may cause overexposure, which is a portion where the printing ink is not attached. As a result, a portion to which a large amount of printing ink adheres and a portion to which only a small amount of printing ink adheres to cause color unevenness.
[0009]
Further, when the roll is strongly pressed against the foam plate in order to eliminate the overexposure, the foam plate buckles at a weak cell wall, and the shape of the foam plate collapses. Also, when trying to cut the foam board with a guillotine or a slicer, a fragment called a whisker is formed on the cut surface, and the cut surface is not beautiful. Therefore, it has been desired to provide a styrene-based resin foam plate which does not cause any inconvenience during such processing.
[0010]
[Problems to be solved by the invention]
The present invention has been made in response to the above-mentioned needs. That is, the present invention uniformly foams at a high magnification and has fine bubbles, the surface is smooth and has a good appearance, and when printed directly on the surface with a roll, it is uniform without causing overexposure and color unevenness. It is intended to provide a styrene-based resin foam that can be printed beautifully, and does not produce whiskers even when cut with a guillotine or slicer, and the cut surface is beautiful and easy to process afterwards. is there.
[0011]
[Means for solving the problem]
The present inventor uses various materials to solve the above-described problems, performs extrusion foaming of the styrene resin under various conditions, and performs post-processing such as printing or cutting on the obtained styrene resin foam. Tried to add. As a result, they have found that the above-mentioned problems can be solved only by selecting and using a specific cell regulator, and then performing extrusion foaming in the conventional manner. That is, when extrusion foaming is performed using a tetrafluoroethylene resin powder and a talc powder in a specific ratio as a cell regulator, the obtained foam is uniformly and finely foamed at a high magnification, and the surface is particularly It has been found that the surface becomes smooth, buckling hardly occurs even when the roll is strongly pressed, and no whiskers are generated when cutting with a guillotine or the like. The present invention has been completed based on such findings.
[0012]
The above-mentioned specific ratio means that the tetrafluoroethylene resin powder (hereinafter referred to as F powder) and the talc powder (hereinafter referred to as T powder) are 10 to 70% and 90 to 30% by weight, respectively. %. Among them, F powder and T powder preferably account for 20 to 60% and 80 to 40%, respectively, and most preferably 30 to 50% and 70 to 50%.
[0013]
The foam regulator composed of the F powder and the T powder is added in an amount of 0.05 to 3.0 parts by weight based on 100 parts by weight of the styrene resin. The reason is that if the amount is less than 0.05 part by weight, the nucleating agent effect is weak and the cells of the foam do not become thin. If the amount is more than 3.0 parts by weight, the open cell ratio of the foam increases and the This is because the strength is reduced, or the elongation of the resin is reduced during the production of the foam, and it becomes difficult to produce a wide-width foam plate. Among them, it is preferable to add 0.1 to 2.5 parts by weight of the cell regulator, and it is most preferable to add 0.2 to 2.0 parts by weight.
[0014]
As the F powder, particles having an average particle diameter of 0.01 to 1 μm are preferably used. As the F powder, it is preferable to use a powder in which the above-mentioned particles are not composed of a single piece, but are formed by agglomeration of finer particles to form a cluster like a bud of budo. It is preferable to use a lump that has a size of 1 to 100 μm, more preferably 1 to 30 μm, and more preferably 1 to 10 μm. Is particularly preferred.
[0015]
Heretofore, what has been generally provided as F powder, when observed with a scanning electron microscope, has been such that each particle is composed of one fragment. That is, particles composed of one fragment existed separately. Some of the particles were uniform in size, but most of them were particles of various sizes. In addition, even for small particles, one of the particles had a particle size of about 1 μm, and there was almost no particle smaller than this, and thus most of the particles were large particles having a particle size of 1 μm or more. Some of the large particles had a particle size of several μm.
[0016]
On the other hand, the F powder in which the fine particles are aggregated to form a nodule as described above, when observed with a scanning electron microscope, shows that hundreds to tens of thousands of fine particles are aggregated, It is an irregular shaped baby boomer like a cloud. The fine particles have an average particle size of 0.01 to 1 μm, and the size of the particles is uniform in one variety. Some of the lumps formed by the aggregation of these fine particles are small ones, i.e., about 1 μm, and large ones are about 100 μm or more. Such a baby boomer has a peculiar shape not found in other things. Also, this shape was not so much seen in the conventional F powder.
[0017]
The F powder forming such a nodule is sold, for example, under the trade name TLP10F-1 by DuPont-Mitsui Fluorochemicals. It is said that the F powder sold under this trade name was obtained by emulsion polymerization of ethylene tetrafluoride.
[0018]
T powder is obtained by pulverizing a natural hydrated silicate mineral. Thus, the particles consist of only one fragment. In order to obtain a foam having fine cells according to the present invention, it is preferable to use T powder having an average particle diameter of 1 to 20 μm. Such T powder is sold, for example, by Kihara Kasei under the trade name of SP-GB. In the present invention, such commercially available products can be used.
[0019]
The F powder and the T powder may be mixed in advance at a ratio of 10 to 70% and 90 to 30% by weight, respectively. For this mixing, it is sufficient to simply mix the mixture in a commonly used mixer.
[0020]
The styrene resin that can be used in the present invention is a resin generally called a styrene resin. That is, the styrene-based resin includes a homopolymer of a styrene-based monomer and a copolymer of a styrene-based monomer and another monomer. Styrene-based monomers include styrene, methylstyrene, chlorostyrene, and the like, and other monomers include acrylonitrile, acrylate, butadiene, and the like. Therefore, typical styrene resins are polystyrene, styrene / butadiene copolymer, and styrene / acrylonitrile copolymer.
[0021]
Among these styrenic resins, the one most frequently used as a panel for decoration and display is a styrene homopolymer, that is, polystyrene. In order to foam a high-quality foamed board by foaming at a high magnification among polystyrene, the melt mass flow rate measured by the method specified in JIS K 7210 is 4 to 15 g / 10 min, and among them, 5 to 10 g / 10 Is preferably used, and particularly preferably 6 to 9 g / 10 minutes.
[0022]
In order to mix the foam control agent composed of the F powder and the T powder with the styrene resin, the mixing means that has been used can be used as it is. That is, the styrene-based resin, the F powder, and the T powder may be directly mixed, or the F powder and the T powder may be each made into a masterbatch with a styrene-based resin and mixed. Preferred is the latter. This is because the latter is easier to disperse the respective powders in the styrene-based resin and does not deteriorate the working environment due to the scattering of the powders.
[0023]
As the foaming agent, those which have been used for foaming styrene resins can be used. That is, carbon dioxide, nitrogen, inorganic compounds such as water, propane, butane, lower aliphatic hydrocarbons such as pentane, methyl chloride, halogenated aliphatic hydrocarbons such as chlorodifluoroethane, dimethyl ether, such as diethyl ether Either ethers or ketones such as acetone can be used.
[0024]
Among these blowing agents, it is preferable to use propane, butane, pentane, neopentane, and dimethyl ether alone or in combination, or to use a mixture of these with carbon dioxide as the blowing agent. In particular, it is preferable to use a mixture of isobutane of 65 to 100% by weight and normal butane of 0 to 35% by weight as butane. The amount of these foaming agents varies depending on the expansion ratio of the foam to be obtained, but generally speaking, 0.5 to 20 parts by weight, preferably 1 to 15 parts by weight, per 100 parts by weight of the styrene resin. , Most preferably 1.5 to 10 parts by weight.
[0025]
The foaming agent is pressed into the styrene-based resin that has been heated and melted in the extruder from a pressure inlet of the foaming agent provided in the barrel of the extruder. The styrene resin into which the foaming agent has been press-fitted is well kneaded so that the foaming agent is uniformly dispersed, and becomes a styrene resin melt containing the foaming agent. The melt is then gradually cooled while uniformly kneading until it exhibits a viscosity suitable for foaming. When the styrenic resin melt has a viscosity suitable for foaming, the melt is extruded from a mold attached to the extruder tip into a low pressure region (usually under atmospheric pressure). The extruded melt immediately foams into a foam. At this time, the foam may have a rod shape, a plate shape, or a tubular shape depending on the shape of the extrusion hole of the mold.
[0026]
An extruder that has been used for extrusion foaming of a styrene resin can be used. That is, any of a single-screw extruder, a twin-screw extruder, and a tandem extruder obtained by combining these extruders can be used. As the extruder, it is necessary to use an extruder capable of melting the styrene-based resin well, uniformly dispersing the cell regulator therein, and dispersing the foaming agent uniformly. It is preferable to use a resin capable of uniformly cooling a molten resin containing a foaming agent to a temperature suitable for foaming.
[0027]
In carrying out the present invention, in addition to the above-described materials, various additives that have been used in performing extrusion foaming can be added. For example, an antistatic agent, an ultraviolet absorber, a flame retardant, a dye, a thermal deterioration inhibitor, and the like can be added.
[0028]
An object of the present invention is to provide a foam which has a smooth surface and can be easily printed after printing. Many of such foams have a plate shape. There are various methods for obtaining such a plate-like foam. For example, extrude in a plate shape using a mold having slit-shaped extrusion holes corresponding to the width and thickness of the plate, or extrude using a mold having an annular extrusion hole, and cut out the extruded circular tube. There is a method of making a plate.
[0029]
In order to efficiently produce a plate-shaped foam with high expansion ratio, use a mold with an annular extrusion hole, and crush the resin extruded from the mold into a flat shape to flatten the inner surfaces. It is preferable that the sheet is fused. A method for producing such a plate-like foam is described, for example, in JP-A-6-226812. The high-temperature tubular foam extruded in this manner is inflated into a balloon by a gas deviating from the foam or a gas blown from a mold. At this time, the size of the balloon can be adjusted by the amount of the foaming agent, the roll take-up speed, and the like, but can also be adjusted by the amount of compressed air or gas injected directly into the balloon. The obtained balloon-like foam is sandwiched between a pair or several pairs of rolls while the inner surface is still warm while being taken off, the inner surface is fused and formed into a plate shape, and then cooled to form a plate-like shape. A foam that has been foamed to a magnification can be manufactured.
[0030]
The foam board thus obtained has high strength in the extrusion direction and the width direction (direction perpendicular to the extrusion direction), and in order to obtain a foam board with a good balance of strength, not only in the extrusion direction but also in the width direction. The foam needs to be stretched. Therefore, it is preferable to adjust the maximum circumferential length of the balloon to be 2 to 4 times the circumferential length of the extrusion hole of the mold. At this time, the maximum substantially circumferential length of the balloon can be obtained by doubling the width of the narrowed plate-shaped foam. When the plate-like foam thus produced is used as a decorative or display panel, the foaming ratio is preferably 7 to 25 times, more preferably 9 to 20 times. The preferred thickness is 3 to 15 mm, more preferably 3.5 to 10 mm.
[0031]
In extrusion foaming, the number and size of cells in the obtained foam vary depending on the types and amounts of the foaming agent and the nucleating agent, and also vary depending on the shape of the extruder, the extrusion die and the foam. For example, in the case of making a round rod-shaped foam using an extrusion die having a circular extrusion hole, and in the case of obtaining a tubular foam using an extrusion die having an annular extrusion hole, The round bar-shaped foam will have finer cells than the tube-shaped foam. This is because a round rod-shaped foam does not apply a large force to pull the foam, but a tubular foam has a large force applied to pull the foam, so that the cells expand and become larger.
[0032]
According to the method of the present invention, when a resin containing a foaming agent is extruded into a tube, the extruded tubular body is crushed flat, and the inner surfaces thereof are laminated to form a foamed plate. It has a unique bubble structure that cannot be seen. That is, in the conventional bonded foam board obtained by using a cell regulator such as talc, although the bubbles in the surface layer are finer than the inside, the fusion layer formed by fusion is also in the surface layer. As in the case of (1), fine bubbles are included, so that the presence of the fused surface is remarkably visible. However, in the bonded foam board obtained by the method of the present invention, although the bubbles in the surface layer are finer than the inside, the fused layer is in the same bubble state as the inside, and the presence of the fused surface is almost not recognized. It cannot be obtained.
[0033]
As described above, in the styrene-based resin foam board obtained by the method of the present invention, the bubbles on the surface are uniformly fine, and the valleys between the bubbles are shallow and narrow, and the fine Because there is no fusion layer containing bubbles, when the foam plate is pressed from the surface with a roll, the foam plate does not buckle with the fusion layer, when printed on the surface of the foam plate with a roll, Printing can be performed uniformly without overexposure and uneven color. In addition, when cutting with a guillotine or a slicer, whiskers are not generated. The foam board manufactured by the method of the present invention has such characteristics.
[0034]
The above-mentioned cell structure of the foamed board obtained by the method of the present invention will be described more specifically below. First, the foam board is cut in the thickness direction perpendicular to the extrusion direction, and an electron micrograph of the cut surface is taken. In the photograph, the average cell diameter at a position 0.25 mm from the surface of the foam plate was Amm, the average cell diameter at a position 0.25 mm from the fusion surface was Bmm, and the surface of the foam plate and the fusion surface The average bubble diameter at the intermediate position of is set to Cmm. Then, this foam board satisfies the following two equations.
0.1 ≦ A / B ≦ 0.8 [Equation 1]
0.8 ≦ B / C ≦ 1.2 [Equation 2]
[0035]
Of these,
0.2 ≦ A / B ≦ 0.6
0.9 ≦ B / C ≦ 1.1
Is preferably satisfied. Here, A satisfies A <0.20.
[0036]
In such a foamed board, since the bubble diameters other than near the surface of the foamed board are almost equal and large, the foamed board has strength, and since the bubble diameter near the surface is small, the valley between the bubbles on the surface becomes narrow and shallow. Good surface smoothness. Therefore, printing can be performed without overexposure or color unevenness by using a roll, and the cutting ability with guillotine or the like is excellent. The surface hardness at this time is 75 or more when the thickness is 5 to 8 mm and the expansion ratio is 10 to 18 times, and the 5% compressive strength is 0.18 MPa or more.
[0037]
In a styrene-based resin foam, the finer the bubbles of the foam, the smoother the surface. However, the finer the bubbles, the thinner the thickness of the cell membrane and the lower its strength. Even if the bubbles are fine in the surface layer portion, the strength of the bubble film decreases little due to an external cooling effect and the like, but the strength of the bubble film particularly decreases in the fusion portion. As a result, it is easy to buckle, and when cut with a guillotine blade or the like, the bubble film is easily broken, and the processed surface of the fused portion becomes dirty. By maintaining the cell diameter in the relationship of the above formulas (1) and (2), a foam plate having excellent printability and cutting processability can be obtained.
[0038]
When the ratio of the F powder to the T powder used as the cell regulator is 100% by total weight, the ratio of the F powder is 70% by weight or more and the ratio of the T powder is 30% by weight or less. The foam structure of the foam
0.8 <A / B ≦ 1.0
0.8 ≦ B / C ≦ 1.2
It becomes. This means that the average cell diameters of A, B and C are almost the same size, and the cell diameter near the surface in the thickness direction of the foam is large. The surface hardness at this time is 75 or more and the 5% compressive strength is 0.18 MPa or more in the foam having a thickness of 3 to 8 mm and an expansion ratio of 10 to 18 times, and is strong and excellent in machinability. However, the appearance of the foam surface is not sufficient, and the printed surface may be overexposed.
[0039]
When the proportion of the F powder is 10% by weight or less and the proportion of the T powder is 90% by weight or more, the cell structure of the obtained foam is as follows:
0.8 ≦ A / B ≦ 1.2
B / C <0.8
It becomes. That is, the bubbles near the foam surface are fine and the appearance of the foam is good, but the bubbles at the interface of the fused portion of the foam are also fine, the bubble film is thin and the bubbles are easily buckled, and the foam has low strength. When printing is directly performed with a roll or the like, color unevenness or the like occurs, resulting in poor printability. Further, the cutting workability becomes poor due to whiskers. The surface hardness at this time is less than 75 and the 5% compressive strength is less than 0.18 MPa for a foam having a thickness of 5 to 8 mm and an expansion ratio of 10 to 18 times.
[0040]
Here, the position at which the average cell diameter A is measured is set to 0.25 mm from the foam surface. At a position close to the epidermis of less than 0.25 mm, the cells are also subjected to external cooling during the cell formation step to form cells. In general, the bubble diameter becomes smaller as it approaches the skin, but as the limit depth at which the bubble diameter affects the surface smoothness, the surface smoothness is good unless the bubble diameter becomes smaller from this area toward the skin. Because it does not become. If the surface is strongly cooled to improve the surface smoothness and the bubbles are made finer, the growth of the bubbles is suppressed and the skin portion becomes non-foamed. In this case, the foam is liable to be cracked, and a suitable cushioning property on the printing surface is lost. Therefore, it is preferable to avoid strong cooling of the surface and to make air bubbles fine to obtain surface smoothness.
[0041]
Further, when the average cell diameter A on the surface of the foam exceeds 0.20 mm, the cell diameter of the surface layer becomes coarse even if the above inequalities of Expressions 1 and 2 are satisfied, and the desired effect cannot be obtained.
[0042]
Further, the position at which the average cell diameter B is measured is set to a position 0.25 mm from the surface where the inner surface of the tube is fused, because the inner surface of the tube at the time of molding is located at a position close to the fused surface of less than 0.25 mm. It is susceptible to the effect of crimping when fusing, and bubbles are not appropriate because they are crushed. .
[0043]
Further, the intermediate position is a position where the cell diameter, which is a reference when confirming the cell structure obtained by the foaming nucleating agent effect, is confirmed, and is a position where the above-mentioned various influences are least likely to occur.
[0044]
The foam having the above-mentioned average cell diameters A, B, and C satisfying 0.1> A / B is difficult to manufacture and has low manufacturing efficiency. Foams satisfying 0.8 <A / B have insufficient surface smoothness. Foams satisfying 0.8> B / C tend to have reduced strength during printing and whiskers during cutting. It is difficult to produce a foam having 1.2 <B / C by a normal production method.
[0045]
【The invention's effect】
According to the present invention, the F powder and the T powder are used as the cell regulator in a ratio of 10 to 70% and 90 to 30% by weight, respectively, and the total amount of the cell regulator is 0 to 100 parts by weight of the styrene resin. 0.05 to 3.0 parts by weight, and the mixture is melted in an extruder. A foaming agent is press-fitted into the extruder and kneaded. Then, the resin in a molten state is extruded from the extruder to a low-pressure region to foam. Thus, a desired styrenic resin foam can be obtained at once. The foam thus obtained is foamed uniformly and finely and has a good appearance, and since the bubbles on the surface are much finer than the inside, the valleys generated between the bubbles are narrow and shallow, Further, since the bubbles near the fusion surface and the middle portion are almost equal, when printed on the surface with a roll, no overexposure or color unevenness occurs. Therefore, a beautiful decorative body can be obtained by printing.
[0046]
Further, when the foamed board is cut with a guillotine or a slicer, the foamed board does not generate whiskers, so that the cutting becomes easy and the cut surface becomes beautiful. Therefore, processing is easy and a beautiful decorative body can be easily made.
[0047]
A foam which is preferable as a foam for display or decoration is a foam which is foamed 7 to 25 times and has a thickness of 3 to 15 mm. According to the method of the present invention, it is possible to easily produce a foam having a desired expansion ratio and thickness within this range. The present invention provides such benefits.
[0048]
Hereinafter, the method of the present invention and the reason why the method is excellent will be specifically described with reference to examples and comparative examples. In that case, the average foam is measured for the obtained foam, the printability is evaluated, the 5% compressive strength and the surface hardness are measured, and the appearance and cutting workability are evaluated. Will be described. In addition, since the particle size of F powder is measured, the measuring method will be described.
[0049]
Average bubble diameter
Using a scanning electron microscope S-3000N (manufactured by Hitachi, Ltd.), a 20-times enlarged photograph of a section obtained by cutting the foam vertically in the width direction (a direction perpendicular to the extrusion direction) is taken. An arbitrary 50 bubbles on a straight line at each measurement position are selected, and the maximum chord length in the width direction and the maximum chord length in the thickness direction of each bubble are measured. The average maximum chord length was determined, and the bubble diameter in each direction was calculated.
Average maximum chord length = sum of arbitrary 50 maximum bubble chord lengths in each direction on a straight line at each measurement position / 50;
Bubble diameter = average maximum chord length / 0.616
The average cell diameter was calculated from the arithmetic mean of the cell diameter derived from the average maximum chord length in the width direction and the cell diameter derived from the average maximum chord length in the thickness direction at each measurement position on the obtained straight line.
[0050]
Printability evaluation
Printing was performed on the surface of 25 foams cut out to 148 mm x 100 mm using a print Gokko B6 set (manufactured by Riso Kagaku) as a printing machine and a silk screen oil-based ink (manufactured by Taiyo Seiki) as a printing paint. At that time, the amount of ink used for printing one sheet was 1.26 g, and evaluated according to the following criteria.
：: Almost no overexposure or color unevenness is observed in 25 of the 25 sheets.
Δ: Overexposure or uneven color was observed in some places on 1 to 5 sheets out of 25 sheets.
×: Overexposure or color unevenness was observed in some places on 6 to 25 sheets out of 25 sheets.
[0051]
5% compressive strength
It was measured according to the method described in JIS K 7220: 1999 “Compression test of foamed plastic-hard material” and evaluated according to the following criteria.
：: 5% compressive strength of 0.18 MPa or more.
×: 5% compressive strength is less than 0.18 MPa.
Here, the 5% compressive strength refers to a test piece size of 50 × 50 × 25 mm using a Tensilon universal testing machine UCT-10T (manufactured by Orientec Co., Ltd.), a compression speed of 10 mm / min, and a 5% compression strength. This is a value obtained by measuring the compressive strength. (Specimen size: A specimen cut out at 50 × 50 in the extrusion direction and width direction of the foam was used as a test piece, and the test was performed so that the thickness of the specimen was 25 mm or more and closest to 25 mm according to the thickness of the foam at that time. Lay the pieces together.)
The compressive strength was calculated by the following equation. The specified deformation is 0.1.
σm = Fm / S0 × 10 ³ σm: compressive strength (kPa)
Fm: Maximum load (N)
S0: Initial cross-sectional area of test piece (mm ² )
[0052]
surface hardness
The surface hardness was measured according to JIS K 7312. The spring hardness test was performed using a spring hardness tester ASKER C (manufactured by Kobunshi Keiki Co., Ltd.) and evaluated according to the following criteria.
：: The surface hardness is 75 or more.
×: Surface hardness is less than 75.
[0053]
Average particle size
The average particle size (average particle size of primary particles) of the ethylene tetrafluoride resin is determined by photographing the ethylene tetrafluoride resin with a scanning electron microscope and arbitrarily selecting 100 primary particles photographed. The major diameter (longest diameter) of the primary particles was measured, and the average value of the 100 particles was defined as the average particle size of the tetrafluoroethylene-based resin. Similarly, the lump of the aggregate of the tetrafluoroethylene-based resin (primary particles) was similarly photographed with a scanning electron microscope, and 100 lump photographed were arbitrarily selected. The longest diameter was measured, and the average value of those 100 pieces was used as my value.
[0054]
Machinability
In the width direction with respect to the extrusion direction of the foam, the cutting is performed with a rotary blade provided with 12 long holes having a diameter of 320 mm, a blade width of 3 mm, a width of 10 mm, and a length of 50 mm and provided with heat radiation processing, and visually observe a cut surface of the foam. And evaluated according to the following criteria.
：: Almost no beard is seen on the cut surface of the foam.
X: A beard is seen on the cut surface of the foam.
[0055]
Embodiment 1
Polystyrene (manufactured by A & M Styrene, trade name: 680 melt mass flow rate: 7.3 g / 10 min) was used as the polystyrene resin, and 100 parts by weight of this resin was mixed with a powder of an ethylene tetrafluoride resin (manufactured by DuPont-Mitsui Fluorochemical Co., Ltd.). Trade name TLP10F-1, average particle size of primary particles 0.25 μm, melting point 325 ° C., bulk density 0.35 g / cm ³ , An emulsion polymerization product) and 0.3 part by weight of talc powder (TALC SP-GB, trade name, manufactured by Kihara Kasei Co., Ltd., average particle size: 3.5 μm) were mixed by a tumbler mixer.
[0056]
This mixture was fed to a hopper of a tandem-type extruder in which the diameter of the first-stage single-screw extruder was 50 mm and the diameter of the second-stage single-screw extruder was 65 mm, melted and kneaded. From the middle of the process, butane was injected as a blowing agent at a ratio of about 6% by weight to obtain a foamable molten resin. At that time, the extruder temperature at the injection portion of the foaming agent was 200 ° C., and the injection pressure was 15 MPa.
[0057]
The screw of the first-stage extruder used had a dull mage portion in order to enhance the effect of melt-kneading and mixing the molten resin, the foam nucleating agent, and the foaming agent. After the foamable molten resin is melt-mixed in the first and second extruders, a mold having an annular extrusion hole attached to the tip of the second extruder (hereinafter referred to as a circular die) ) (70 mm diameter, mold gap 0.76 mm), while extruding the foam into the atmosphere into a balloon and blowing compressed air (gauge pressure 0.1 MPa), the deflection plate (maximum opening) sandwiched away from the die While being shaped into a plate at an interval of 300 mm and a minimum opening interval of 30 mm), it was passed between rolls to fuse the inner surface of the balloon-like foam to produce a take-off plate-like foam.
[0058]
The obtained foam had a width of 290 mm, a thickness of 7 mm, a beautiful appearance, an expansion ratio of 16 times, and a cell structure in the thickness direction of A 0.15, A / B 0.63, and B / C 0.96. The bubble diameter of the surface layer was remarkably smaller than the bubble diameter of the fusion interface layer. Table 1 shows the evaluation results of the obtained plate-like foam having a surface hardness of 79, a 5% compressive strength of 0.26 MPa, a sheet appearance, printability, and cutting workability.
[0059]
Embodiment 2
Polystyrene (manufactured by A & M Styrene, trade name: 680 melt mass flow rate: 7.3 g / 10 minutes) was used as the polystyrene resin, and 100% by weight of this resin was mixed with a 20% masterbatch (base resin) of ethylene tetrafluoride resin powder. 1.5 parts by weight (trade name: HRM10, manufactured by Toyo Styrene Co., Ltd.) and 0.75 parts by weight of a 40% master batch of talc powder (base resin: HRM10, manufactured by Toyo Styrene Co., Ltd.) were mixed by a tumbler mixer. A foam was produced from this mixture in the same manner as in Example 1. As a powder of the ethylene tetrafluoride resin of the master batch, a trade name of MP-1100 (manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd .; ³ , Emulsion polymerization products). TALC SP-GB (average particle size: 3.5 μm) manufactured by Kihara Kasei Co., Ltd. was used as the talc powder of the master batch. The substantial amount of each powder is that the base resin of the masterbatch is a polystyrene resin, and when calculated, about 0.295 parts is used for 100 parts by weight of the styrene resin.
[0060]
The obtained foam had a width of 290 mm, a thickness of 7 mm, a beautiful appearance, an expansion ratio of 16 times, and a cell structure in the thickness direction of A 0.15, A / B 0.60, and B / C 0.93. The bubble diameter of the surface layer was remarkably smaller than the bubble diameter of the fusion interface layer. The obtained plate-like foam had a surface hardness of 76 and a 5% compressive strength of 0.20 MPa. Table 1 shows the evaluation results of printability and cutting workability.
[0061]
[Comparative Example 1]
A foam was produced in the same manner as in Example 1 except that the nucleating agent to be added was only 0.6 parts by weight of the same ethylene tetrafluoride resin powder as in Example 1. The obtained foam had a width of 290 mm, a thickness of 7 mm, an expansion ratio of 16 times, and a bubble structure in the thickness direction of A 0.21, A / B 0.88, and B / C 1.00. The difference in the average cell diameter was small, and the surface layer had a slightly coarse cell structure accordingly. The obtained plate-like foam had a surface hardness of 76 and a 5% compressive strength of 0.22 MPa. Table 1 shows the evaluation results of printability and cutting workability.
[0062]
[Comparative Example 2]
A foam was produced in the same manner as in Example 1 except that the nucleating agent to be added was only 0.6 parts by weight of the same talc powder as in Example 1. The obtained foam had a width of 290 mm, a thickness of 7 mm, a beautiful appearance, an expansion ratio of 16 times, and a cell structure in the thickness direction of A 0.15, A / B 1.14, and B / C 0.45. Both the adhesion interface layer and the surface layer had a structure in which the bubble diameter was fine. The resulting plate-like foam had a surface hardness of 71 and a 5% compressive strength of 0.12 MPa. Table 1 shows the evaluation results of printability and cutting workability.
[0063]
[Table 1]

[Brief description of the drawings]
FIG. 1 is a scanning electron micrograph of a fine powder of an ethylene tetrafluoride resin used in Example 1. From this photograph, it can be seen that the primary particles aggregated in a budo shape to form a lump.
FIG. 2 is a scanning electron micrograph of a fine powder of an ethylene tetrafluoride resin having a primary particle diameter of 15 μm.
FIG. 3 is a scanning electron micrograph of a cross section of the foam obtained in Example 1. From this photograph, it can be seen that in the cell structure in the thickness direction of the foam, the cell diameter of the surface layer is particularly small, and the cell diameter of the fusion interface layer is not small.
4 is a scanning electron micrograph of a cross section of the foam obtained in Comparative Example 2. FIG. From this photograph, it can be seen that in the cell structure in the thickness direction of the foam, the cell diameters of the surface layer and the fusion interface layer are particularly small.

Claims (6)

With respect to 100 parts by weight of the styrene-based resin, 0.05 to 3.0 parts by weight of a cell adjuster composed of an ethylene tetrafluoride-based resin powder and a talc powder was compounded as a total amount, and the obtained compound was subjected to an extruder. A method for producing a styrene-based resin foam in which a resin in a molten state is extruded from an extruder into a low-pressure region to be foamed after being melted, press-fitted with a foaming agent, and kneaded. A method for producing a styrenic resin foam, wherein the proportions of the fluorinated ethylene resin powder and the talc powder are 10 to 70% and 90 to 30% by weight, respectively. At the tip of the extruder, a mold with an annular extrusion hole is attached, and the resin in the molten state is formed into a tube from the annular extrusion hole and extruded into a low-pressure region, and the inner surface of the tubular body is still at a high temperature. The method for producing a styrenic resin foam according to claim 1, wherein the tubular body is pressed flat in the middle and the inner surface is fused to form a thick foam. The method for producing a styrene resin foam according to claim 1 or 2, wherein particles having an average particle diameter of 0.01 to 1 µm are used as the ethylene tetrafluoride resin powder. As the tetrafluoroethylene-based resin powder, fine particles having an average particle size of 0.01 to 1 μm are aggregated to form a lump of 1 to 100 μm. The method for producing a styrene resin foam according to claim 3. A laminated foamed resin plate formed by flattening a tubular styrene-based resin melt containing a foaming agent and fusing the inner surface, and the fused surface is in the same bubble state as the inside of the remaining resin plate. The styrene-based resin foam plate is characterized in that the entire inside of the resin plate is in a uniform foamed state. The styrene resin foam plate according to claim 5, wherein the surface of the foam plate is finely and uniformly foamed from the inside, and the valleys between cells on the surface are narrow and shallow.

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