JP2002086577A - Foamed synthetic resin and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed synthetic resin excellent in appearance, touch, handling, smoothness, adhesion, etc., after the resin is cut and its skin layer is removed and a method for producing the foamed synthetic resin. SOLUTION: In the foamed synthetic resin, at least one main surface has no skin layer and has exposed bubbles and an angle of repose measured by a method given in the specification of 55 degrees or below, or the opening area of exposed bubbles of the main surfaces of the resin is at least 50% of the surface area of the resin. The surface of the resin is cut by a knife edge.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin foam and a method for producing the same, and more particularly, to a resin having good surface properties, good handling, good dimensional accuracy, and high adhesive strength to other materials. And a method for producing the same.

2. Description of the Related Art A synthetic resin foam is formed by molding a foamed resin, for example, a foam of a thermoplastic resin such as a polystyrene resin is melt-extruded and molded, and a thermosetting resin is heated and foamed in a mold. Then, a skin layer is formed on the surface. This skin layer is generally a smooth surface on which no air bubbles are exposed. However, in the case of a plate material or the like, the thickness is increased in order to increase the productivity, improve the thickness accuracy, and improve the adhesion with other materials. It is common practice to cut out a molded product to a desired thickness to produce a product. In addition, the skin layer itself is removed for the purpose of improving the thickness accuracy and improving the adhesiveness to other materials.
For example, in heat insulation construction in reinforced concrete construction or steel reinforced reinforced concrete construction, the adhesion of the synthetic resin foam to concrete is ensured by removing the skin layer to expose the air bubble portion. Conventionally, such a cutting operation of a synthetic resin foam or a work of removing a skin layer is performed by cutting a thermoplastic resin foam with a hot wire, and generally using a saw or a canner for woodwork. Have been done.

However, in the case of the synthetic resin foam cut by a saw or a canner for woodworking as described above, the cutting powder remains on the surface, which makes it difficult to handle. As the smoothness is not enough, not only is the commercial value of the appearance such as touch and aesthetics low,
Poor dimensional accuracy, iii) Chips penetrated into bubbles exposed on the surface, or bubble films exposed on the surface were cut or broken by a conventional saw or canner, and were damaged or exposed. There has been such a problem that the bubble film is covered by the bubbles, and the adhesive strength with other materials is poor. That is, the value as a product in both appearance and performance was low. Even when synthetic resin foam is hot-wire cut, chips are not generated,
The same is true in that the surface is not smooth and the bubbles exposed on the surface are melted and broken to form a thin skin layer, which lowers the adhesive strength. Therefore, the present invention provides a synthetic resin foam excellent in appearance, touch, handling, smoothness, adhesiveness, and the like even when performing a cutting operation or a skin layer removing operation of the synthetic resin foam, and a method of manufacturing the same. It is intended to do so.

DISCLOSURE OF THE INVENTION The present invention has been accomplished by finding that the above-mentioned problems of the prior art can be solved by cutting a synthetic resin foam using a knife blade. Thus, according to the present invention, there is provided in particular: (1) At least one main surface has no skin layer, air bubbles are exposed, and the angle of repose (rest angle) measured by the method described in the specification is 55 degrees or less, preferably 50 degrees or less, more preferably Is at most 48 degrees, especially at most 46 degrees. (2) The synthetic resin foam according to (1), wherein the opening area of the exposed cells (open cells) on the main surface has an area ratio of 50% or more to the surface area of the synthetic resin foam. (3) A synthetic resin foam characterized in that the opening area of the exposed cells on at least one main surface has an area ratio of 50% or more to the surface area of the synthetic resin foam. (4) The synthetic resin foam according to (1) to (3), wherein the synthetic resin foam is made of a polystyrene resin. (5) The synthetic resin foam of (1) to (4), wherein the main surface is a surface cut by a knife blade. (6) When the cell size in the thickness direction of the synthetic resin foam is V, the cell size in the width direction is H, and the cell size in the length direction is P, 0.5 ≦ V / P ≦ 1.5, 0 .5 ≦ V / H ≦ 1.5
The synthetic resin foam of (1) to (5) satisfying the following relationship: (7) The average cell diameter of the synthetic resin foam is 0.05 to 1.0
mm, and the density of the synthetic resin foam is 16 to 60 kg /
synthetic resin foam of m is ³ (1) to (6). (8) The synthetic resin foam is cut with a knife blade (especially a band saw of a knife blade) to cut at least one of the synthetic resin foam.
A method for producing a synthetic resin foam, comprising forming two main surfaces. (9) The method for producing a synthetic resin foam according to (8), wherein the synthetic resin foam comprises a polystyrene resin. (10) The method for producing a synthetic resin foam according to (8) or (9), wherein the angle of repose measured by the method described in the specification of the main surface formed by the cutting is 55 degrees or less. (11) The method for producing a synthetic resin foam according to any one of (8) to (10), wherein the synthetic resin foam having the characteristics of the above (2), (6) and (7) is formed. (12) A synthetic resin foam produced by the production method of (8) to (11).

BEST MODE FOR CARRYING OUT THE INVENTION The synthetic resin foam which can be used in the present invention is not particularly limited, and a polystyrene resin,
Polyethylene-based resin, polypropylene-based resin, polyurethane-based resin, phenol-based resin and the like can be exemplified, among which polystyrene-based resin, polyethylene-based resin, polypropylene-based resin and the like that can be prepared by extrusion foaming method are preferable, Further, a polystyrene resin excellent in heat insulation and low mechanical strength is particularly preferable. Examples of the polystyrene resin include, for example, styrene, α-methylstyrene, chlorostyrene, dichlorostyrene, dimethylstyrene, t-butylstyrene, a styrene derivative such as vinyltoluene, or a copolymer comprising a combination of two or more of these. Or a copolymer thereof with a compound which can be easily polymerized with another such as acrylic acid, acrylic ester, methacrylic acid, maleic anhydride, or butadiene. The synthetic resin foam of the present invention has at least 1
One of the main surfaces has no skin layer, air bubbles are exposed, and the angle of repose (rest angle) measured by the method described below is 55 degrees or less. The main surface where the bubbles are exposed without the skin layer is a surface obtained by cutting the synthetic resin foam once formed or finishing the surface and removing the skin layer, particularly cutting. It means a surface obtained by processing. When having a skin layer, the angle of repose can be 55 degrees or less, but this is not the purpose. In the skin layer, bubbles are generally crushed and not exposed. The main surface may be any surface that has been cut, but refers to a surface having a large surface area, particularly the upper and lower surfaces of a plate material. According to the present invention, conventionally, when cutting with a saw or a canner for woodwork, processing marks (surface roughness) on the cutting surface,
Although generation of cutting powder was inevitable, it was found that when cutting was performed with a knife blade, a clean surface with little processing traces (rough surface) and little generation of cutting powder was obtained. As a result of repeated studies, by selecting a cutting tool and cutting conditions, the appearance is beautiful, there is almost no processing mark (rough surface) and little cutting powder, excellent smoothness, It has been confirmed that a synthetic resin foam having a surface excellent in adhesiveness can be obtained, and the present invention has been completed. And it was confirmed that such a novel synthetic resin foam according to the present invention can be characterized by having a repose angle (rest angle) measured by the method described below of 55 degrees or less.
In the present invention, the angle of repose (rest angle) of the synthetic resin foam is
As shown in FIG. 1, two sheets of synthetic resin foam (the size of the lower synthetic resin foam is the same as or larger than that of the upper synthetic resin foam) with the main surfaces of the synthetic resin foam in question facing each other. 1a and 1b are overlapped, and the two sheets are placed on the table 2. The lower synthetic resin foam 1a is fixed with the stopper 3, and the angle of the table is gradually increased. Angle θ at which the synthetic resin foam 1b slips down
Is defined. However, the weight of the upper synthetic resin foam is 0.25 g / cm ² per surface area when the foam is placed horizontally. The adjustment of the load may be performed by changing the thickness of the foam, or may be performed by applying a weight so that the foam is evenly applied. According to the present invention, the surface of the synthetic resin foam formed by selecting a cutting tool and cutting conditions using a knife blade has almost no cutting marks (surface roughness) as in the case of cutting with a conventional light saw, The bubbles are cut cleanly and the breakage of the bubble wall is extremely small, and the surface is extremely smooth (compare the photographs of FIGS. 4 and 5 and 6). for that reason,
When the surface of the synthetic resin foam of the present invention is observed with an electron microscope, it can be easily identified as a surface cut with a knife blade, particularly a surface cut with a band saw of a knife blade. Therefore, whether or not it is the synthetic resin foam of the present invention can be basically identified by observing the surface with an electron microscope, but the present invention defines or limits the characteristics of the surface by the angle of repose. FIG. 2 schematically shows a difference between a surface of a synthetic resin foam cut with a knife blade according to the present invention and a surface of the synthetic resin foam cut with a conventional saw, as a cross-sectional view perpendicular to the cut surface. FIG. 2 (a) shows a case where an ideal cut is made. On the other hand, as can be seen in the figure, the surface of the synthetic resin foam formed (cut, cut) by the method of the present invention is As shown in FIG. 2B, the bubble (cell) 5 on the processing surface is hardly deformed, and the flatness (flatness) and smoothness of the cut surface are maintained, and the end 6a of the bubble wall 6 is maintained. Is only slightly deformed. On the other hand, as shown in FIG. 2 (c), the surface of the synthetic resin foam cut by a conventional light saw blade is
The cut surface is rough, not flat, and the cell walls 6c on many surfaces are crushed and the open cells 5c are also broken. The difference between the cut surfaces is seen in the electron micrographs of FIG. 4 and FIGS. The angle of repose of the synthetic resin foam of the present invention is 55 degrees or less, preferably 50 degrees or less, more preferably 48 degrees or less, particularly 46 degrees or less. The smaller the angle of repose, the better the surface properties (smoothness, plane roughness) and the maintenance of the related bubble structure (adhesion strength, etc.). The excellent surface properties of the synthetic resin foam of the present invention can also be expressed by the area ratio of the opening area of the exposed cells on the main surface to the surface area of the synthetic resin foam, and this area ratio is 50% or more. It is preferably at least 75%, more preferably at least 85%, especially at least 90%. The larger the area ratio, the less the bubble wall is broken during the cutting process and the smaller the number of cutting marks.
On the surface of the foam cut by the conventional method, the cell wall is broken, and the area of the open cell is reduced, but the cell wall cut by the method of the present invention has a small open cell area ratio of the open cell. . In the measurement of the opening area, if the cell wall of the cell is substantially crushed, even if such a cell wall remains, it is not regarded as an open cell, that is, is not included in the opening area. The measurement of the area ratio of the opening area of the exposed bubbles to the surface area of the synthetic resin foam is performed by taking a photograph of the surface of the synthetic resin foam with an electron microscope and calculating the total area of the opening areas of the exposed bubbles.
The area ratio may be calculated by dividing the total area value by the surface area of the synthetic resin foam. As a method for calculating the total opening area of the exposed bubbles from the electron micrograph, a method of placing a tracing paper on the photograph, filling the open cell portion, and calculating the total area of the open cells can be used. The total area of the open cells may be obtained by counting grids of grid paper using tracing paper as grid paper, or may be calculated by a computer using a monochrome analysis system. The density of the synthetic resin foam of the present invention is preferably from 16~60kg / ^{m 3,} more preferably from 20 to 50 kg / ^{m 3.} The density of the synthetic resin foam is a value obtained by dividing the weight of the foam by the volume. When the density of the synthetic resin foam is higher than 60 kg / m ³ , the cost increases and the resistance at the time of cutting increases, making the processing difficult. On the other hand, when the density is lower than 16 kg / m ³ , the mechanical strength is reduced and the dimensional stability is poor. The average cell diameter of the synthetic resin foam of the present invention is preferably 0.05 to 1.0 mm, and more preferably 0.15 to 0.8 mm. Here, the average cell diameter refers to an average value obtained by dividing the sum of the cell diameters (average values) in the thickness, width, and length directions of the synthetic resin foam by three. The cell diameter of the synthetic resin foam is ASTM-D-356.
Measure according to the method specified in 7. Average bubble diameter is 1.0mm
If it is larger, the radiation is increased and the thermal conductivity is inferior, and the diameter of the open cell on the surface is increased, so that the surface has a rough texture. In addition, the average bubble diameter is 0.
If the thickness is smaller than 05 mm, the thickness of the bubble film becomes thin, and the bubble film is easily deformed, resulting in poor smoothness. Further, when the cell size in the thickness direction of the synthetic resin foam of the present invention is V, the cell size in the width direction is H, and the cell size in the length direction is P, 0.5 ≦ V / P ≦ 1.5 , 0.5 ≦ V / H ≦
It is preferable to satisfy the relationship of 1.5. More preferred ranges are 0.8 ≦ V / P ≦ 1.3, 0.8 ≦ V / H ≦ 1.
3. Here, the cell diameter in the thickness, width and length directions of the synthetic resin foam means the cell size (average value) measured in each direction. This is because, in a synthetic resin foam having cells satisfying such conditions, the machinability is further improved. A spherical shape having substantially the same size of bubbles in three directions is preferable from the viewpoint of cuttability and dimensional stability. V / P or V / H
Is larger than 1.5, the number of bubble films in the cutting direction increases, so that the cut surface is easily roughened, and V / P or V / H
Is smaller than 0.5, the width and length dimensions shrink due to the stress action that relaxes the stretching generated in the cell membrane, resulting in poor dimensional stability. As described above, the synthetic resin foam of the present invention can be obtained by forming a surface by cutting using a knife blade. In particular, when cutting is performed using a band saw with a knife blade, a synthetic resin foam having extremely excellent surface properties can be obtained. Conventional cutting with a hot wire or woodworking band saw or rotary saw could not obtain a surface having the above characteristics.However, when cutting using a knife blade band saw, as shown in the example, Thus, a synthetic resin foam having extremely excellent surface characteristics (aesthetic appearance, surface smoothness, high open cell area ratio, etc.) was obtained. In conventional saws and the like, "cutting" is performed, but in the case of the band saw of the knife blade of the present invention, it is also called a band saw, but there is no setting like a conventional saw, it is a knife blade to the last, so "cut with a knife blade" The surface itself is obtained. A clean cut surface can be obtained as in the case of cutting vegetables and meat with a knife blade. Cutting a synthetic resin foam using a knife blade (especially a band saw of a knife blade) as described above is a novel invention that has not been conventionally performed. In addition, it was confirmed that the same effect can be obtained also in the case of the flattening processing (canna processing, planar processing) using a knife blade. In this flattening process, one or several arbitrarily twisted knife blades are attached to a rotating body, and a workpiece is inserted into a device in which the rotating body (which can be called a planar knife) is vertically arranged. By doing so, the cutting by the knife blade is repeatedly performed intermittently. Therefore, one cutting with one knife blade is "cut with a knife blade", so it is similar to cutting using a band saw of a knife blade, but the knife blade rotates and intermittently contacts the surface of the workpiece. Therefore, the continuous cutting action by the knife blade in the case of cutting using the band saw of the knife blade is not the same. However, in general, it is possible to obtain the surface characteristics of the cutting surface close to the cutting process using the band saw of the knife blade, and in particular, by selecting the type of the planar knife and the working conditions, the characteristic values defined in the present invention are satisfied. It was confirmed that it was also possible to obtain a synthetic resin foam having surface characteristics. As described above, the knife blade itself for cutting synthetic resin foam according to the present invention is already provided and marketed for materials other than synthetic resin, for example, for meat and bread slicing and metal canner processing. May be selected from those available, or specially developed, designed, and manufactured. For example, a band saw having a thickness of about 1 mm and a width of about 100 mm can be used as a knife blade. In addition, as a planar knife, a flattening tool commercially available from Kanebo Co., Ltd. Block with a built-in knife blade) or the like can be used. The shape and material of the knife blade are not particularly limited, and may be selected in consideration of the type of the synthetic resin foam, the processing machine, and the processing conditions. The method of cutting and cutting may be a combination of the conventional method of processing a synthetic resin foam and the method of processing (processing with a knife blade) used in the present invention. Conventionally, a foam 11 obtained by shaving the upper and lower skin surfaces of a cooled synthetic resin foam raw wood with a woodworking canner (abrasive canner) is sliced through a band saw 12 as shown in FIG.
A product with a predetermined thickness has been obtained. At this time, by changing the number of saw blades of the band saw, slicing can be performed at a time on a few sheets or the like. According to the present invention, a predetermined thickness is obtained by cutting the upper and lower skin surfaces of a cooled synthetic resin foam raw wood using a planar knife and then slicing the same through a band saw of a knife blade. Products can be obtained. Further, the foam produced by the above-mentioned conventional method may be passed through a planar knife or a knife saw to cut the surface thinly to finish the surface secondary processing.

As described above, the synthetic resin foam provided by the present invention is not only beautiful in appearance but also free of cutting chips and has excellent surface properties and dimensional accuracy as compared with conventional synthetic resin foams. Therefore, it can be suitably used not only for ordinary heat insulating materials but also for displays. In addition, since the ratio of the exposed bubbles is large, a high adhesive strength with other materials can be obtained by the emboss effect (anchoring effect).

EXAMPLES (Example 1) According to a conventional method for producing a polystyrene resin foam by an extrusion method, predetermined amounts of a polystyrene resin, a physical foaming agent, a pigment, a cell regulator, and a lubricant were supplied to a screw-type melt extruder. The gel uniformly kneaded in the extruder was passed through a cooling device, and the cooled foamable gel was extruded into the atmosphere from a die orifice to form a foam raw wood having a predetermined cross-sectional area. After the production, the foam raw wood (105 mm thick, 980 mm wide, 1850 mm long) cooled to room temperature was sliced into three pieces of 30 mm thick using a band saw with a saw blade.
The sliced foam plate was passed through a band saw machine with a knife blade (blade thickness: 1 mm, width: 100 mm) to cut the surface to obtain a plate-like foam having a thickness of 25 mm. The physical properties of the obtained plate-like polystyrene foam were measured by the following methods. (Bubble diameter) Measured according to ASTM D 3567. (Density) Foam density = foam weight / foam volume (area ratio of foam exposed on the surface to foam cross-sectional area)
A black-and-white photograph of the surface of the synthetic resin foam is taken with a scanning electron microscope, a tracing paper (grid paper) is placed on the photograph, and the open cell portion is painted out to calculate the total area of the open cell. The total area of the open cells may be calculated by counting the grids of the graph paper and calculating the ratio of the open cells, or may be calculated by a computer using a monochrome image analysis system. The total area of the calculated open cells is divided by the total cross-sectional area of the foam to obtain an area ratio. (Surface properties) The surface properties were evaluated by a four-stage evaluation of ◎, △, Δ, and × on the degree of roughness and smoothness of the surface by touch. The sensory test showed a clear difference. (Repose angle / rest angle) As shown in FIG. 1, two synthetic resin foams 1a and 1b are overlapped with the main surfaces of the synthetic resin foam facing each other, and the two And the lower synthetic resin foam 1a is fixed with the stopper 3 to gradually increase the angle of the table, and the angle θ of the table at the time when the upper synthetic resin foam 1b slips down.
Was measured. However, the upper synthetic resin foam had a length in the inclined direction of 150 mm and a width of 100 mm, and the weight of the foam was 0.25 g / cm ² per surface area when the foam was placed horizontally. The dimensions of the lower synthetic resin foam were larger than those of the upper foam. This load was adjusted by changing the thickness of the foam and applying a weight so that the foam was evenly applied. Table 1 shows the results. FIG. 4 shows a scanning electron micrograph of the surface of the polystyrene resin foam after cutting with a knife blade. (Examples 2 to 5, Reference Example 1 and Comparative Examples 1 to 3) For a polystyrene resin foam produced in the same manner as in Example 1, but having different densities as shown in Table 1, the method of surface cutting was as follows. With the above modification, a plate-like polystyrene resin foam was produced in the same manner as in Example 1. Example 1 Band saw (knife blade) Example 2 Band saw (knife blade) Example 3 Planar knife Example 4 Band saw (knife blade) Example 5 Band saw (knife blade) Comparative Example 1 Abrasive grain Comparative Example 2 Band saw (saw) Blade) Comparative Example 3 Belt Sander The knife blade used here is sharp and continuous.
It is a simple knife. A saw blade is a blade that has a sharp edge. The planar knife has a knife blade on the circumference of the rotating body and is used by rotating the knife blade (in this case, the knife blade is formed to be twisted with respect to the rotating body). The abrasive grain canna is a canna in which diamond particles are scattered on a spiral mountain of rollers. The belt sander is a polishing belt using minerals as abrasive grains. The physical properties of the obtained plate-like polystyrene resin foam were evaluated in the same manner as in Example 1. Table 1 shows the results. Comparative Examples 2 and 3
FIGS. 5 and 6 show scanning electron micrographs of the surface of the polystyrene resin foam after the cutting process. From these photographs, as compared with the photograph of Example 1 in FIG. 3, the cut portion of the cell wall of the resin foam was crushed and the flatness (probably also the smoothness) was reduced. It can be easily seen that the number of open cells is significantly reduced.

[Table 1] From Table 1, according to the present invention, the angle of repose is 55 degrees or less (50 degrees or less, and even 44 degrees), and the area ratio of the opening area of the exposed bubbles on the main surface to the surface area of the foam is 50% or more (85% It is recognized that a synthetic resin foam excellent in surface properties can be obtained. More specifically, a synthetic resin foam having extremely excellent surface properties could be obtained by at least cutting using a band saw with a knife blade. Also, besides the band saw of the knife blade, when cutting using a knife blade like a planar knife,
By appropriately setting the cutting conditions and depending on the type of the synthetic resin foam, a synthetic resin foam having similarly excellent surface properties could be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for measuring the angle of repose of a synthetic resin foam.

FIG. 2 is a schematic explanatory view of various cut surfaces of a synthetic resin foam.

FIG. 3 is a diagram illustrating a state of cutting a synthetic resin foam.

FIG. 4 is a scanning electron micrograph of the synthetic resin foam of Example 1.

FIG. 5 is a scanning electron micrograph of a synthetic resin foam of Comparative Example 2.

FIG. 6 is a scanning electron micrograph of the synthetic resin foam of Comparative Example 3.

[Explanation of symbols]

 1a ... lower synthetic resin foam 1b ... upper synthetic resin foam 2 ... base 3 ... stopper 5 ... bubbles (cells) 5c ... collapsed bubbles 6 ... bubble walls 6a ... set of bubble walls

Claims (10)

[Claims] 1. A synthetic resin foam characterized in that at least one main surface has no skin layer, air bubbles are exposed, and a repose angle measured by a method described in the specification is 55 degrees or less. . 2. The synthetic resin foam according to claim 1, wherein the opening area of the exposed cells on the main surface has an area ratio of 50% or more to the surface area of the synthetic resin foam. 3. The open area of the exposed cells of at least one main surface is 50% of the surface area of the synthetic resin foam.
A synthetic resin foam having the above area ratio. 4. The synthetic resin foam according to claim 1, wherein the synthetic resin foam comprises a polystyrene resin. 5. The synthetic resin foam according to claim 1, wherein the main surface is a surface cut by a knife blade. 6. When the cell size in the thickness direction of the synthetic resin foam is V, the cell size in the width direction is H, and the cell size in the length direction is P, 0.5 ≦ V / P ≦ 1.5. , 0.5 ≦ V / H ≦
The synthetic resin foam according to any one of claims 1 to 5, which satisfies the relationship of 1.5. 7. The synthetic resin foam has an average cell diameter of 0.05.
And the density of the synthetic resin foam is 16 to 6 mm.
The synthetic resin foam according to claim 1 which is 0 kg / ^{m 3.} 8. A method for producing a synthetic resin foam, comprising cutting the synthetic resin foam with a knife blade to form at least one main surface of the synthetic resin foam. 9. The method for producing a synthetic resin foam according to claim 8, wherein the synthetic resin foam comprises a polystyrene resin. 10. The method for producing a synthetic resin foam according to claim 8, wherein the angle of repose of the main surface formed by the cutting process, measured by the method described in the specification, is 55 degrees or less.