JP3278269B2 - Plate-shaped laminated thermoplastic resin molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate-shaped laminated thermoplastic resin molded article having a small warp.

[0002]

2. Description of the Related Art Thermoplastic resins are used after being processed into various molded articles in a wide range of fields. Plate-shaped thermoplastic molded products are generally manufactured by injection molding.For example, a plate-shaped thermoplastic resin molded product having different material properties from the front surface and the back surface is located on one side first. It is manufactured by molding a thermoplastic resin and then molding the thermoplastic resin on the other side.

[0003]

However, according to this method, the thermoplastic resin on one side molded earlier has already shrunk to some extent because it has been molded and solidified first, and the thermoplastic resin on the other side molded later has the same properties. Since the previously molded thermoplastic resin is molded after shrinking to some extent, there is a large difference in the shrinkage ratio between the two. Therefore, when the shape of the thermoplastic resin molded article is a plate-like body, the molded article has a great disadvantage that a large amount of warpage occurs after a certain period of time, and the dimensional accuracy over time becomes extremely poor. Therefore, it has been a major problem to prevent warpage of the plate-shaped laminated thermoplastic resin molded article and to obtain a molded article having good dimensional accuracy.

[0004]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the above-mentioned problems, and as a result, using a thermoplastic resin having a different flexural modulus as a thermoplastic resin constituting a plate-like laminated thermoplastic resin molded article, The inventors have found that the above problem can be solved by setting the cross-sectional area occupied by each resin in a cross section cut along a plane parallel to the thickness direction to a value in a specific range, and have led to the present invention.

That is, the present invention relates to a plate-like molded product in which two kinds of thermoplastic resins having different flexural modulus and a flexural modulus ratio of 0.5 or less are laminated, 2 in at least one section cut in a plane parallel to
The boundary between the kinds of thermoplastic resins has unevenness, and the cross section satisfies the following expressions (1) and (2) at the same time.

0.2 <B / A ≦ 1.6 (1) 0.5 ≦ (C × I) / (A × I ′) <1 (2) (where, A: Cross-sectional area occupied by a thermoplastic resin having a high flexural modulus.

B: Cross-sectional area occupied by a thermoplastic resin having a low flexural modulus.

C: Total cross-sectional area of the plate-shaped laminated thermoplastic resin molded article.

I: Secondary moment of area of the thermoplastic resin having a high flexural modulus with respect to an axis passing through the center of the thermoplastic resin having a high flexural modulus and perpendicular to the thickness direction and existing in the cross section.

I ': Second moment of area of the plate-shaped laminated thermoplastic resin molded product with respect to an axis passing through the center of the plate-shaped laminated thermoplastic resin molded product and perpendicular to the plate thickness direction and existing in the cross section. The thermoplastic resin constituting the plate-shaped laminated thermoplastic resin molded article of the present invention has a different flexural modulus, and the ratio of the flexural modulus of these thermoplastic resins is 0.5 or less. . That is, one surface of the plate-shaped laminated thermoplastic resin molded article is a thermoplastic resin having a high flexural modulus (hereinafter, also referred to as a high rigidity thermoplastic resin), and the other surface is a thermoplastic resin having a low flexural modulus. Resin (hereinafter, also referred to as a low-rigidity thermoplastic resin). And, the ratio of the respective bending elastic moduli of the low-rigidity thermoplastic resin and the high-rigidity thermoplastic resin (low-rigidity thermoplastic resin / high-rigidity thermoplastic resin) must be 0.5 or less, and 0.3 or less. Preferably, there is. If the flexural modulus ratio exceeds 0.5, the residual stress due to the difference in shrinkage between the high-rigidity thermoplastic resin and the low-rigidity thermoplastic resin cannot be reduced by the low-rigidity thermoplastic resin, and We cannot prevent warpage.

In the present invention, the thermoplastic resins to be laminated are preferably of the same type, for example, polyolefins and polyamides, in order to improve the adhesion between the two. Further, as a high rigidity thermoplastic resin, the flexural modulus is 10,000 to 100,000 kg /.
Since the warpage of the molded article tends to be particularly large when a resin having a size in the range of cm ² is used, the effect of the present invention becomes remarkable when such a thermoplastic resin is used. Also,
When the above-mentioned high-rigidity thermoplastic resin is used, the low-rigidity thermoplastic resin for reducing warpage may have a flexural modulus of 40.
It is preferable to use one in the range of 0 to 15,000 kg / cm ² .

[0012] The thermoplastic resin used in the present invention is not particularly limited, and a known thermoplastic resin can be used. For example, polyolefins such as polyethylene, polypropylene and polybutene; polystyrene, AS resin (acrylonitrile-styrene copolymer), ABS resin (acrylonitrile-butadiene-styrene copolymer)
Styrene polymers such as nylon; nylon 6, nylon 66
Polyamide; and halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride.
These thermoplastic resins can be used alone or in combination. In the present invention, a crystalline resin such as polyamide or polyolefin is particularly suitable,
In particular, when polypropylene is used, it is preferable because the effect of reducing warpage is large.

The plate-shaped laminated thermoplastic resin molded article of the present invention comprises:
In at least one section cut along a plane parallel to the plate thickness direction, the boundary between the above-described high-rigidity thermoplastic resin and the low-rigidity thermoplastic resin has irregularities. The cross section of the plate-shaped laminated thermoplastic resin molded article of the present invention cut along a plane parallel to the plate thickness direction has a number of cross sections corresponding to the number of the planes. In the present invention, as long as at least one of the cross sections satisfies the requirements described later, the other cross sections do not necessarily have to satisfy the requirements.

The shape of the unevenness of the boundary in the above-mentioned cross section is not particularly limited, and may be any of a shape combining straight lines, a shape combining curves, and may be symmetrical or unsymmetrical. Specifically, FIGS.
And irregular shapes such as a comb shape, a wavy shape, and a combination thereof. When the boundary in the cross section is not uneven but straight as shown in FIG. 10, the residual stress due to the difference in contraction between the high-rigidity thermoplastic resin and the low-rigidity thermoplastic resin cannot be reduced by the low-rigidity thermoplastic resin, It is not possible to prevent warping of the molded body.

Further, in the present invention, it is necessary to satisfy the following expressions (1) and (2) at the same time in the cross section.

0.2 <B / A ≦ 1.6 (1) 0.5 ≦ (C × I) / (A × I ′) <1 (2) A: Cross-sectional area occupied by a thermoplastic resin having a high flexural modulus.

B: Cross-sectional area occupied by a thermoplastic resin having a low flexural modulus.

C: Total cross-sectional area of the plate-shaped laminated thermoplastic resin molded article.

I: Second moment of area of the thermoplastic resin having a high flexural modulus with respect to an axis passing through the center of the thermoplastic resin having a high flexural modulus and perpendicular to the thickness direction and existing in the cross section.

I ': The second moment of area of the plate-shaped laminated thermoplastic resin molded product with respect to the axis passing through the center of the plate-shaped laminated thermoplastic resin molded product and perpendicular to the plate thickness direction and existing in the cross section. The centroid in the above equation represents the center of gravity in the cross-sectional shape, and the second moment of area is defined in the Mechanical Engineering Handbook (May 15, 1988, published by The Japan Society of Mechanical Engineers), A4, page 24. Index of the flexural rigidity
One. In the present invention, the area moment of inertia is calculated using commercially available software such as “I-DE” manufactured by SDRC.
AS VI. i "can be easily calculated. A relatively simple shape can also be calculated using the above-mentioned formulas for various cross-sectional shapes listed in Table 6 on pages 25-26 of the Mechanical Engineering Handbook A4.

In the above equation, equation (1) represents the cross-sectional area ratio of the low-rigidity thermoplastic resin to the high-rigidity thermoplastic resin.
When this value is small, the high-rigidity thermoplastic resin suppresses the shrinkage of the low-rigidity thermoplastic resin to be molded later, which means that the effect of suppressing the warpage of the plate-shaped laminated thermoplastic resin molded article is large. Equation (2) is obtained by dividing the second moment of area per unit cross-sectional area of the high-rigidity thermoplastic resin by the second moment of area per unit cross-sectional area of the plate-shaped laminated thermoplastic resin molded product. That is, when the value calculated by the equation (2) increases, the flexural rigidity per unit cross-sectional area increases, indicating that the effect of suppressing the warpage of the plate-shaped laminated thermoplastic resin molded article is large.

In the present invention, B / A must be more than 0.2 and not more than 1.6 as shown by the above formula (1), and preferably not more than 1. If B / A exceeds 1.6, the effect of the high-rigidity thermoplastic resin to suppress the residual stress due to the difference in shrinkage between the high-rigidity thermoplastic resin and the low-rigidity thermoplastic resin decreases, so that the plate-like laminating heat is reduced. It is not possible to prevent warping of the plastic resin molded article. B / A is 0.2
In the following cases, warpage hardly occurs, and it goes without saying that the present invention is followed.

Further, in the present invention, the above formula (2)
(C × I) / (A × I ′) must be 0.5 or more and less than 1 as shown by, and it is preferable that the value approaches 1 as much as possible, but the effect of the present invention is 0.7 or more. Notable.
When the value of the above formula (2) is less than 0.5, the high-rigidity thermoplastic resin and the low-rigidity thermoplastic resin cannot sufficiently obtain the effect of suppressing warpage between each other. We cannot prevent warpage. Further, when the value of the above formula (2) is 1 or more, it is not preferable because it is difficult to form a laminated molded body in shape. In addition, when the above equation (2) has the same value, it is preferable that the boundary line in the cross section be longer.

The thermoplastic resin used in the present invention may contain additives such as conventionally known heat stabilizers, weathering agents, coloring agents, antistatic agents, lubricants, nucleating agents, and blooming inhibitors;
Calcium carbonate, mica, barium sulfate, glass fiber,
Inorganic fillers such as glass beads, glass balloons, carbon fibers, etc .; organic fillers such as wood powder, fir powder, pulp; polybromodiphenyl ether represented by decabrom diphenyl ether; TBA derivatives; TBS derivatives; bromine-containing isocyanuric acid derivatives; Brominated organic flame retardants; various phosphoric acid flame retardants; and inorganic flame retardants such as antimony trioxide, magnesium hydroxide, aluminum hydroxide, and red phosphorus.

The term “plate shape” in the plate-shaped laminated thermoplastic resin molded article of the present invention means that the length in the thickness direction is relatively shorter than the length in the vertical and horizontal directions, and the direction parallel to the thickness direction of the plate. Can be any shape, for example, not only a square and a rectangle, but also a polygon such as a triangle, a quadrangle, and a pentagon, a circle, a hollow circle (a donut shape), a semicircle, a hollow semicircle, an arc shape, and a hollow circle. It may be arc-shaped, horseshoe-shaped, crescent-shaped, or the like. In addition, the cross-sectional shape in the thickness direction is also an arbitrary shape, for example, in addition to a rectangle,
Polygons such as triangles, squares, pentagons, oblongs, bows,
It may be a crescent moon or the like. Further, the surface may be subjected to a special unevenness processing, and may be any as long as it has a substantially plate-like shape.

The method for producing the plate-shaped laminated thermoplastic resin molded article of the present invention is not particularly limited, and known injection molding, press molding, extrusion molding, stampable molding and the like can be employed. In particular, in the injection molding, in the case of the core back method or the two-color molding method, after filling one side of the mold with a high-rigidity thermoplastic resin, after retracting the mold core, or after inverting the mold, A method of filling the other side with a low-rigidity thermoplastic resin can be adopted.

Also, a method in which a high-rigidity thermoplastic resin is molded in one mold in advance, the molded body is taken out, and then attached to the other mold, and a low-rigidity thermoplastic resin is filled. it can. When this method is adopted, the difference between the effect according to the present invention and the effect otherwise is large, and the effect of the present invention is large.

[0028]

The plate-shaped laminated thermoplastic resin molded article of the present invention is a molded article having good dimensional stability without deformation due to warpage. The reason why such an effect is obtained is that the ratio of the bending elastic modulus of the high-rigidity thermoplastic resin and the low-rigidity thermoplastic resin constituting the plate-shaped laminated thermoplastic resin molded article is a specific value,
Since the boundary in the cross section of these thermoplastic resins has an uneven shape, and furthermore, the cross section satisfies a specific formula, the molded article of the high rigid thermoplastic resin molded earlier has a low rigidity molded later. It is presumed that this is because deformation due to shrinkage of the molded article of the thermoplastic resin is suppressed.

Therefore, the plate-shaped laminated thermoplastic resin molded article of the present invention is useful as various members requiring dimensional stability. For example, automobile parts such as bumpers, instrument panels, and door trims; housings for word processors, personal computers, keyboards, copiers, and other OA equipment; housing materials such as door panels, sashes, and wall boards;
It can be preferably used for sanitary parts such as toilet lids.

[0030]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

The thermoplastic resins shown in Examples and Comparative Examples and those already described with reference to the symbols in the table are as follows.

Thermoplastic resin: Symbol Material Flexural modulus (kg / cm ² ) A: Propylene homopolymer 20,000 B: Ethylene propylene block copolymer 15,000 C: Ethylene propylene random copolymer 10,000 D: Ethylene propylene block copolymer Polymer 5,000 E: Ethylene propylene block copolymer 3,000 Symbol in the table: L: Boundary line length in cross section.

L ': Boundary line length of the test piece in FIG.

Examples and Comparative Examples Molding of plate-shaped laminated thermoplastic resin molded articles and measurement of warpage were performed as follows. A molded product was obtained based on the following molding method, and warpage was measured. The results are shown in Table 1. In addition, the second moment of area is “I-DEAS V” manufactured by SDRC.
I. i ".

(A) Molding Method Using a high rigidity thermoplastic resin, an injection molding machine with a 150T vent manufactured by Nippon Steel Works, Ltd. under the following conditions, width 60 mm × length 260
mm test pieces were obtained.

Injection molding temperature (cylinder temperature setting) 230 ° C. Die temperature (cooling water temperature setting) 40 ° C. The cross-sectional shapes of these test pieces cut along a plane parallel to the plate thickness direction and the width direction are shown in FIG. (A), (b), (c), (d), (e), (f),
(G), (h) and (i). The dimensions of the cross section are indicated by numerals in each figure.

Next, the flat surface of the test piece is brought into close contact with the mold, and a 60 mm wide × 260 mm long × 6 mm thick is formed so that the low-rigidity thermoplastic resin is newly filled in the uneven surface space on the opposite side. Attached to the mold. Next, a low-rigidity thermoplastic resin is filled with the same injection molding machine as above under the same conditions, and (a ′), (b ′), (c ′), (d ′),
(E '), (f'), (g '), (h') and (i ') were obtained, each having a width of 60 mm, a length of 260 mm and a thickness of 6 mm. In FIGS. 10 to 18, the black portion is a high-rigidity thermoplastic resin, and the white portion is a low-rigidity thermoplastic resin.

(B) Method of Observing Warpage of Molded Product After the laminated molded product obtained as described above has been molded for 48 hours, it is placed on a horizontal plate, and one side of the lower surface of the laminated molded product is measured from a horizontal plane. The farthest distance was measured.

[0039]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a sectional view of a high-rigidity thermoplastic resin molded body of a comparative example.

FIG. 2 is a cross-sectional view of a high-rigidity thermoplastic resin molded product of an example.

FIG. 3 is a cross-sectional view of a high-rigidity thermoplastic resin molded body of a comparative example.

FIG. 4 is a cross-sectional view of a high-rigidity thermoplastic resin molded product of an example.

FIG. 5 is a sectional view of a high-rigidity thermoplastic resin molded product of an example.

FIG. 6 is a sectional view of a high-rigidity thermoplastic resin molded product of an example.

FIG. 7 is a cross-sectional view of a high-rigidity thermoplastic resin molded article of an example.

FIG. 8 is a cross-sectional view of a high-rigidity thermoplastic resin molded product of an example.

FIG. 9 is a sectional view of a high-rigidity thermoplastic resin molded product according to an example.

FIG. 10 is a sectional view of a plate-shaped laminated thermoplastic resin molded product of a comparative example.

FIG. 11 is a cross-sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

FIG. 12 is a sectional view of a plate-shaped laminated thermoplastic resin molded product of a comparative example.

FIG. 13 is a cross-sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

FIG. 14 is a cross-sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

FIG. 15 is a cross-sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

FIG. 16 is a cross-sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

FIG. 17 is a cross-sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

FIG. 18 is a sectional view of a plate-shaped laminated thermoplastic resin molded product of an example.

Claims (1)

(57) [Claims] 1. A plate-like molded product in which two kinds of thermoplastic resins having different flexural modulus and a flexural modulus ratio of 0.5 or less are laminated, and a plane parallel to the plate thickness direction. The boundary between the two types of thermoplastic resin in at least one cross section cut in step (a) has irregularities, and the cross section satisfies the following expressions (1) and (2) simultaneously. Plastic molded article. 0.2 <B / A ≦ 1.6 (1) 0.5 ≦ (C × I) / (A × I ′) <1 (2) (where, A: Cross-sectional area occupied by thermoplastic resin having high flexural modulus B: Cross-sectional area occupied by thermoplastic resin having low flexural modulus C: Total cross-sectional area of plate-shaped laminated thermoplastic resin molded article I: High flexural modulus Second moment of area of the thermoplastic resin having a high flexural modulus with respect to an axis passing through the centroid of the thermoplastic resin and perpendicular to the thickness direction and existing in the cross section I ': Drawing of plate-shaped laminated thermoplastic resin molded article The moment of inertia of the plate-shaped laminated thermoplastic resin article with respect to an axis passing through the center and perpendicular to the thickness direction and present in the cross section.)