JPH0354607B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to a unit of a certain volume such as a tape cassette for a video tape recorder, a floppy disk, a video disk, a digital audio disk, and a photosensitive material. Circular, square, or rectangular thin sheet products such as sheet film, photographic paper, IC printed boards, etc. are wrapped individually or in multiples in bags or outer paper to form a set of fixed volume. The present invention relates to a method for producing a thermoplastic resin container having an approximately cubic or rectangular parallelepiped shape (bookcase shape) and having an open opening on one side, for accommodating an approximately cubic or rectangular product. Small thermoplastic resin containers can be three-dimensionally molded by direct injection molding, but in the case of cases that store items over a certain volume, such as tape cassettes for video tape recorders, ,
It is possible to perform three-dimensional molding by direct injection molding by creating a large draft angle, but this not only causes large deformations such as warpage and sink marks and has a bad appearance, but also causes the product to be housed to wobble and not be fixed firmly. It may fall while being carried, and
Three-dimensional injection molded products are bulky and difficult to transport and
Storage costs are high, making it impossible to put it into practical use.

In addition, because the front, back, and left and right sides are in the direction of mold removal, it is not possible to create irregularities on the surface of the container. is also used, but its dimensions change depending on humidity, it curls and warps occur, its compressive strength decreases under high humidity, it is also expensive, and the fibers fall off during use. , the problem of sticking to the product occurs.

Furthermore, as the number of uses increases, there is a problem in that the degree of deterioration increases as the paper is made of paper.

As an improvement method for this, the present inventor invented and filed an application for a method of manufacturing a container made of synthetic resin, which is characterized in that a developing plate made of synthetic resin having a diagonal line part and a notch part is made by injection molding, and this is made into a box. (Special Application No. 58-26007).

[Purpose of the invention]

The present invention further improves the prior invention by the applicant, and in addition to being able to change the transparency, the present invention is made on a sheet, so the volume is less than 1/10 of a three-dimensional molded product, and the storage cost of packaging materials is reduced. Thermoplastics are advantageous in terms of efficiency, cost, and environmental protection, as they can significantly reduce transportation costs and eliminate the need for cutting, punching, and embossing, reducing the occurrence of defective products, production losses, and man-hours. The purpose of the present invention is to provide a method for manufacturing a resin container.

The object of the present invention is to further improve the prior art as described above, and to improve the shot shot, weld line, and It is an object of the present invention to provide a method for manufacturing a thermoplastic resin container with wires by an injection molding method (including an in-mold injection molding method), which can greatly reduce the occurrence of warpage, kinks, flow marks, sink marks, etc.

[Structure of the invention]

The above-mentioned object of the present invention is a method for producing a container made of a thermoplastic resin, in which a developing plate made of a thermoplastic resin and having at least a diagonal line portion is created by injection molding (including vacuum injection molding in a mold), and this is manufactured into a box. (a) the average thickness of the expansion plate is 0.3 to 3 mm; (b) the average thickness of the diagonal line portion is 15% or more thinner than the average thickness of the expansion plate; (c) The resin injection port (gate) is located on the bottom, surface, back, or side of the flap (cross section).
This is achieved by a method for manufacturing a thermoplastic resin container, characterized in that the container has at least one location on the bottom surface and the bottom surface is 10% to 150% thicker than the front and back surfaces.

Hereinafter, the present invention will be explained in more detail with reference to the accompanying drawings.

In the present invention, as shown in FIG.
is the development plate 2 shown in Figures 2 and 3, or the development plate 2 shown in Figures 4 and 4.
It is manufactured by forming a developing plate 2' shown in FIG. 5 into a box.

In FIGS. 2 and 3, the development plate 2 includes a front part 4; a back part 5; a left side part 6; a right side part 7; a bottom part 8; a left side overlapped part 9; a right side overlapped part 1.
0: It consists of flaps 11, 11a and a wire portion 12, and by forming these into a box, a thermoplastic resin container 1 as shown in FIG. 1 is formed. In Figures 2 and 3, 17 is the trace of the injection hole when the thermoplastic resin was injection molded, and the injection hole during injection molding is
The inlet trace 17 is located near the center of gravity P of the developing plate 2 as shown in FIG. 2, or near the symmetrical positions Q and R across the center line CD of the developing plate 2 as shown in FIG. provided. Further, it is preferable that the case is formed so that the injection port trace 17 is located inside the container after the case is formed. In FIG. 1, the correspondence of each part of the expansion plate in FIGS. 2 and 3 is shown except for the flaps 11 and 11a; The injection port may be provided as a side gate in the cross section of the flap (not shown).

In FIGS. 4 and 5, the development plate 2' includes a front part 4'; a back part 5'; a left side part 6'; a right side part 7'; a bottom part 8'; a left side overlapping part 9'; a right side. The overlapping part 10' consists of flaps 11', 11'a and a wire part 12', and by forming these into a box, a thermoplastic resin container 1 as shown in FIG. 1 is formed. 4 and 5, reference numeral 17' indicates the injection hole mark when the thermoplastic resin was injection molded. U near the center of flaps 11' and 11'a on the center line EF, near VN, or symmetrical positions Q, R or U across the center line C'D' of the expansion plate 2' as shown in FIG. , V. It is possible and desirable for the resin injection port (gate) to have a structure that goes slightly inside the plane as shown in FIG. 8 so as not to leave any marks or cause problems even if marks remain. Also, resin injection port trace 17
and 17' may be located anywhere on the bottom surfaces 8 and 8', the flaps 11 and 11a, or 11' and 11'a, such as on the front or back surfaces or cross-sections of the expansion plates 2 and 2'.

The number of resin injection ports (gates) may also be an even number or an odd number. Preferably the center line of the development plates 2 and 2'
Q, R at symmetrical positions across the center of gravity P on EF or E'F' or the center line CD or C'D' of the development plates 2 and 2'
Or U, V. UV or S or T if the resin composition is prone to resin inlet marks (gate marks).
It is desirable to provide the flaps at one or more locations on the front, back, or cross-section of the flaps 11 and 11a or 11' and 11'a that do not appear on the surface of the product.

In the case of a resin composition where weld lines are likely to occur, in the present invention, the bottom portions 8 and 8' are made thicker so that the resin can flow easily, so kinks, warps, and short shots do not occur, so the resin injection port (gate) can be Countermeasures can be taken at certain points. The inlet trace 17' is preferably formed into a case so that it becomes the inside of the container after forming the case. In the present invention, even if traces of the injection port are left on the outside of the container, hardly any traces remain and this poses no problem.

Conventionally, a thermoplastic resin container 1 as shown in FIG.
In the case of a case that stores items over a certain volume, a thermoplastic resin flat plate of a certain thickness that has been extruded into a long length from a T-die is cut and cut as shown in Figure 2.
The notches marked with diagonal lines in Figures 3, 4, and 5 are cut out and shaped, punched out with diamond lines attached, or the notched parts are made into uncut rectangular plates. After that, the highlighted part 12 or 12' is formed by compression shaping or cutting, and then the hatched cutout part 13, 14, 15, 16 or 13', 1 is formed.
4', 15', and 16' were punched, and in some cases, the front part 4 or 4' was stamped to create a development plate, which was then manufactured into a box.

According to the present invention, FIG. 2, FIG. 3, or FIG.
A developing plate 2 or 2' as shown in FIG. 5 is injected from the beginning in a polygonal shape having a notch, a diagonal line part 12 or 12', and, in some cases, an uneven front part. It is produced by molding (including vacuum injection molding) and then made into a box to produce a thermoplastic resin container 1 as shown in FIG.

In the method of the present invention, various thermoplastic resins can be used as the thermoplastic resin to be injection molded. In particular, polyofrein thermoplastic resin, polystyrene thermoplastic resin, ABS thermoplastic resin, or these thermoplastic resins 2 are used. Mixed resins of more than one species are suitable in terms of cost, manufacturing accuracy, dimensional stability, silicon wire strength, suitability for injection molding, etc., and polypropylene resin is particularly suitable. These thermoplastic resins contain various blowing agents, white pigments (titanium oxide, talc, mica, calcium carbonate, clay, etc.), various carbon blacks, various coloring pigments, and various metal powders (aluminum powder, tin powder, etc.). , various organic or inorganic fiber substances such as various metal fibers, glass fibers, and carbon fibers, various other color dyes, various antistatic agents, various silicones, surfactants, lubricants such as sodium stearate, and oxidants. Various known additives such as inhibitors can be added.

Furthermore, when performing injection molding (including in-mold vacuum injection molding) in the method of the present invention, the injection port (gate) for the molten thermoplastic resin is not limited to the single point P in FIG. It is possible to provide multiple tube locations as shown at points Q, R, U, and V in FIGS. 4 and 5. By doing so, the flow of the resin improves during injection molding, and it is possible to prevent the occurrence of a boundary line where resin flows converge, which is called a weld line. These injection ports (gates) are designed to improve the fluidity of the thermoplastic resin in terms of the appearance of the container and, in a structure where the diagonal line is provided only on the surface of the container as shown in Figure 7, the inside of the container (inner surface in contact with the product). It is desirable that the thermoplastic resin be formed at one or more locations on both sides, preferably in the vicinity of horizontally or vertically symmetrical positions, where the thermoplastic resin can flow in approximately the same amount of time as the four corners. In particular, if the injection port (gate) for the thermoplastic resin is to be placed in only one place, it is particularly desirable to have the injection port (gate) in one place, the position of P in Figure 2 and the position of Q in Figure 3.
Or place it at the R position and the U position in FIG.
If you want to make it in two places, make it in the positions Q and R in Figure 3 and in the positions U and V in Figure 4.

In any case, in the present invention, the number and position of the resin injection ports (gates) change depending on the shape of the developing plate, the fluidity (metal index) of the thermoplastic resin, etc., so the invention is not limited to the description of the present invention, and the manufacturing process is not limited to the present invention. It is desirable that it be located inside the container (inner surface side that comes into contact with the product) or on the flap when the container is packaged.

Furthermore, the fluidity during molding can be improved by adding 0.1 to 5% by weight of a silicon compound such as polydimethylsiloxane, a surfactant such as saponin, or a lubricant such as a higher fatty acid metal salt such as sodium stearate to the thermoplastic resin. It is possible to improve the properties, moldability, mold releasability, and slipperiness after molding. Additionally, by adding an antistatic agent to the thermoplastic resin, it is possible to make it difficult for dirt and dust to adhere to the container, or by adding a foaming agent to the thermoplastic resin, the appearance of the container can be changed to improve its feel and make it lighter. It may also be optionally possible to do so.

When manufacturing a thermoplastic resin container 1 as shown in FIG. 1 by the method of the present invention, the development plate 2 or 2' as shown in FIGS. 2 and 3 or 4 and 5 is
It is preferable that the cross-sectional shape is as shown in FIGS. 6 and 7. The plate thickness t is generally from about 0.3 mm to about 3 mm, and by making the wire part thinner by 15% or more with respect to the plate thickness t, it is easier to manufacture the box. In the present invention, the cooling efficiency of the expansion plate 2 or 2' which is an injection molded product,
The board thickness is adjusted to prevent warping, sink marks, and twisting, and to ensure strength.
0.3-3mm preferably 0.5-1.5mm most preferably
The thickness is limited to 0.7 to 1.2 mm, and in order to ensure the fluidity of the thermoplastic resin and at the same time facilitate box manufacturing, the wire section should be thinned by at least 15%, preferably at least 50%, relative to the plate thickness t, from the viewpoint of strength. It is necessary to ensure a thickness of at least 0.07 mm to 1.0 mm, preferably 0.15 to 0.5 mm.

Furthermore, the thickness of the bottom part 8.8' is 10% to 150%, preferably 15% to 60%, of the thickness of the front part 4.4' and the back part 5.5'.
% thicker (Figures 6 to 9), and by providing one or more resin injection ports (gates) on the bottom, front and back surfaces of the flap, or cross-sectional view (side) of the flap, the flow resistance of the resin is reduced. However, if a resin injection port is provided at the bottom, the resin can be made to flow uniformly by reducing the thickness of the wire near the resin injection port.

Bottom parts 8 and 8', front parts 4 and 4', and back part 5
10 to 16 show schematic diagrams of the flow of the thermoplastic resin when the thicknesses of the wire portions 12 and 12' are varied.

When the bottom, front, and back parts have uniform thickness, the flow of thermoplastic resin is as shown in Figures 10 and 11 (when there is one resin injection port) and Figure 12 (when there are two resin injection ports). Depending on the resin composition, warping, twisting, short shots, and flow marks may occur depending on the resin composition. However, as in the present invention, by making the bottom part 10 to 150% thicker than the front and back parts (Figs. 6 to 9), the thermoplastic resin first flows through the bottom part, and then the resin flows through the bottom part. It becomes a flat plate flow that flows through the wires, making warping, twisting, and short shots less likely to occur. Figure 13 and 1
Figure 4 is a schematic flow diagram for these cases, Figure 13 is for one gate, and Figure 14 is for side gate S.
It is a flow schematic diagram when resin is injected from the inside.

Furthermore, by making the wire thickness thinner at the resin injection port and thicker at the resin injection port, the flow speed of the thermoplastic resin is made approximately equal, eliminating warpage, kinks, short shots, weld lines, and flow marks, and improving physical strength. can be improved. 1st
Figures 5 and 16 are schematic diagrams of flow in these cases, and Figure 15 shows the case where the resin injection port is at one location and the side sectional view of the cross-sectional area is as shown in Figures 17, 18, and 19. FIG. Further, FIG. 16 is a flow diagram schematically showing a case where there are two resin injection ports and a side sectional view of the portion shown in FIG. 20 is shown.

Front part 4 or 4'; Back part 5 or 5' before box making;
The outer or inner surfaces of the left side part 6 or 6', the right side part 7 or 7', and the bottom part 8 or 8' are embossed (=grained), grooved, or textured to improve the appearance and ease of handling. Improvements are also made selectively.

As examples of grain shapes, Tokyo Bearon Co., Ltd. presents more than 200 types of "Bearonjibo" processed samples.

In conventional manufacturing methods, these were performed by embossing, but in the method of the present invention, these surface treatments can also be performed during injection molding (including vacuum injection molding).

〔Example〕

Next, in order to further clarify the effects of the present invention, examples are presented below.

(1) A developing plate injection mold as shown in Fig. 2 was prepared. The mold was designed so that the dimensions of the display board were as shown below.

Vertical and horizontal dimensions of the expansion plate: Longest part is 247mm x 237mm Thickness of the expansion plate: Bottom part 1.0mm Others 0.7mm Dimensions of the wire part: Width 1.5mm, depth gate part 0.15mm, maximum 0.45mm
(Fig. 17) Cross-sectional shape of the expansion plate: As shown in Fig. 7 Dimensions of cutouts 13 and 14: Approximately 70 mm in length and 20 mm in width Dimensions of cutouts 15 and 16: Polygonal with the longest part 37 mm x 28 mm (2) Using this mold, a molten thermoplastic resin with the following composition was injection molded: Polypropylene resin manufactured by Mitsui Petrochemicals, Inc., grade No. J-950D (MI-40 g/10 minutes) 97.8% by weight Shin-Etsu silicone Dimethylpolysiloxane manufactured by Co., Ltd.
Brand name KF-96 0.1% by weight Titanium oxide 2% by weight Electrostripper antistatic agent manufactured by Kao Soap Co., Ltd. 0.1% by weight (3) Assemble the injection molded development plates 2 and bond the overlapping parts using an ultrasonic bonding machine. The approximate dimensions are
A case for a videotape cassette measuring 192mm x 105mm x 28mm was manufactured.

When manufacturing 300,000 boxes, the manufacturing cost is reduced by 50% compared to the conventional manufacturing method that involves cutting and punching, and the injection moldability is very good, reducing the incidence of defective products. was almost 0% in the method of the present invention, compared to 11% in the conventional method.

Furthermore, there was almost no occurrence of warpage, kinks, sink marks, weld lines, short shots, or flow marks, making it suitable as a development plate with wires.

〔Effect of the invention〕

According to the method of the present invention, the number of man-hours is reduced as described above, which lowers manufacturing costs and stabilizes the process.
There are no warps, kinks, or weld lines, and you can achieve significant effects such as improving appearance, precision, and finished surface quality, automating work, and reducing industrial waste.

The present invention is not limited to the embodiments, and can be widely applied, for example, as shown below.

(1) The shape of the expansion plate is not bilaterally symmetrical; for example, the shape of the front part and the shape of the back part may be different.

(2) Even if the thickness of the side part is the same as the remaining thickness of the wire part, the strength can be maintained by overlapping joints.

(3) The shape of the notch can be various shapes such as rectangle, square, trapezoid, semicircle, semiellipse, equilateral triangle, isosceles triangle, and arrow shape.

(4) The residual thickness of the wire part may be partially increased to improve suitability for box manufacturing or to improve the flow of resin during injection molding.

(5) Processing the surface of the mold to create a transparent window in one or more places on the development plate, or marking the inner and outer surfaces of the case with the product name, company name, picture, etc.・It can be made to have a pattern (texturing) such as a lattice pattern or fine-grain surface texture.

As for specific grain processing samples, there are over 210 types of "Bearon Shibo" published by Tokyo Bearon Co., Ltd.

(6) For injection molding, the thermoplastic resin can be a copolymer or a mixed resin of two or more thermoplastic resins.

(7) Thermoplastic resins contain 1 color pigment or color dye.
A species or multiple species can be added.

(8) After injection molding the development plate, printing and labeling processes are selectively added before and after the box manufacturing process.
Marks and characters can be attached.

(9) As for injection molding, in addition to the general injection molding method, it is effective to use an in-mold vacuum injection molding method in which the inside of the mold is evacuated and injection molding is performed.

(10) As for the method of attaching the resin injection port (gate), various known methods can be selected in terms of position, number, size, and type, but pinpoint gates and side gates are particularly preferred.

It is important to carefully consider the influence of flow orientation on the shape of the resin injection port (hereinafter referred to as gate) depending on the type of material and the shape of the molded product.

It is preferable that Q and R in FIG. 3 be equally divided points between the center line CD and both left and right sides.

The types (shapes) of resin injection ports (gates) are broadly classified into restrictive gates and non-restrictive gates depending on their functions. Types include multi-point gates, direct gates (sprue gates, tab gates, film gates (also called flash gates or slit gates),
Fan gate, disk gate, ring gate, subliminal gate (tunnel gate),
There are pinpoint gates, etc.

Gate size is a factor directly related to the flow of molten material into the cavity.

If the gate is too small, not only will filling be insufficient (short shot), but the product is likely to have sink marks, discoloration, weld lines, and other appearance defects.

Furthermore, if the gate is small, the molding shrinkage rate tends to increase, and from the viewpoint of the strength of the molded product, it is not preferable for the gate to be too small.

On the other hand, if the gate is too large, excessive residual stress will be generated around the gate, causing product deformation and cracks.

Furthermore, if the gate cross-sectional area is too large, it will take a long time to solidify (gate seal), which is not desirable in terms of molding efficiency, and the appearance will be poor due to the large amount of gate residue and gate attenuation.

It is necessary to consider the points mentioned above.

(11) As examples of runners, gold runners, semi-hot runners, hot runners, etc. can be used.

In gold runner and semi-hot, the runner is generated together with the molded product. On the other hand, a heater is inserted into the sprue and runner parts to prevent the molten resin in these parts from solidifying and to keep it in a fluid state at all times, leaving the runner part in the mold for each shot. The runner-less molds that allow only one part to be taken out are the extension nozzle method (sprue-less structure), the well-type nozzle method (more than one mold), the insulated runner method, and the hot runner method (multiple molds). mold) can be used.

(12) As for the mold, multi-chamfering is realized through injection molding using not only the conventional one-stage (single stack) single-chamfer but also a multi-stage (multi-stacking) mold consisting of two or more stages (double stack). By doing so, it is possible to increase productivity several times and achieve significant cost reductions.

(13) As the thermoplastic resin used in the present invention, polyolefin resin is preferable, as it requires appropriate rigidity and surface strength, and a hinge effect for the wire portion, so polypropylene resin (homotype polypropylene resin, propylene/ethylene/random resin) is preferable. Polymer resins, propylene/ethylene block copolymer resins, propylene and C ₂ - C ₁₀ α olefin block or random copolymer resins, or thermoplastic resins containing 50% by weight or more of the above propylene resins) are preferred, and most preferably various Polypropylene resins, especially propylene/ethylene/random copolymer resins containing 0.01 to 2 parts by weight of various nucleating agents, are suitable for cost, printing suitability, manufacturing accuracy, dimensional stability, wire strength, surface strength, rigidity, suitability for injection molding, etc. It is suitable in terms of.

(14) Methods for printing on the development plate having the above-mentioned line parts and notches can be roughly divided into letterpress printing, planographic printing, intaglio printing, and various known printing methods, preferably silk screen printing, gravure printing, halftone gravure printing, It is effective to use offset printing, curved surface printing (tampo printing), flexographic printing, hot stamping printing (foil stamping printing), etc.

(15) After creating a developing plate with a diagonal line part and a cutout part, print it using the method described in (14) above and apply ink to it using air, heat, hot air, infrared rays, vacuum, ultraviolet rays, electron beam, etc. for 30 minutes. It is possible to force reaction fixation or dry fixation within a practical range.

(16) In the present invention, due to the two-color molding method, the key line part requires a hinge effect, so the above-mentioned (13)
It is also possible to create an injection molded development plate using polypropylene resin, with a transparent window made of highly transparent polystyrene or methyl taacrylate resin for the front or back part.

[Brief explanation of drawings]

FIG. 1 is an external view of a thermoplastic resin container manufactured according to the present invention, FIGS. 2, 3, 4, and 5 are plan views showing embodiments of the expansion plate, and FIGS. FIG. 9 is a sectional view of the developed plate taken along the line A-B in FIGS. 2 and 3 or the plane A'-B' in FIGS. 4 and 5. FIGS. 10 to 16 are schematic diagrams of the flow of thermoplastic resin, and FIGS. 17 to 20 are side sectional views of the portion shown in FIG. 1... Thermoplastic resin container, 2, 2'... Development plate, 4, 4'... Front part, 5, 5'... Back part,
8, 8'...Bottom part, 12, 12'...K line part,
13, 14, 15, 16, 13', 14', 15',
16'... Notch, 17, 17'... Inlet trace.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a thermoplastic resin container, in which a developing plate made of a thermoplastic resin and having at least a diagonal line portion is produced by injection molding, and the same is manufactured into a box, comprising: (a) an average of the developing plate; The thickness is 0.3 to 3 mm, (b) the average thickness of the silicon wire portion is 15% or more thinner than the average thickness of the expansion plate, and the average thickness of the silicon wire portion is 0.07 to 1.0 mm, (c ) There is one or more resin injection ports on the bottom, the front or back of the flap, or the side of the flap, and the thickness of the bottom is 10% or more than that of the front and back.
A method for manufacturing a thermoplastic resin container characterized by making it 150% thicker. 2. The method of manufacturing a thermoplastic resin container according to claim 1, wherein the thickness of the silicone line portion is made 30% or more thinner than the average thickness of the silicone line portion near the resin injection port. 3. The method for manufacturing a thermoplastic resin container according to claim 1, characterized in that the resin injection port portion of the bottom or flap where the resin injection port is provided is made thinner than the surface portion by 0.1 mm or more. 4 The thermoplastic resin is a polyolefin thermoplastic resin, a polyvinyl chloride resin, a polystyrene thermoplastic resin, an ABS thermoplastic resin, a copolymer resin of these resins and another thermoplastic resin, or two types of these thermoplastic resins. The method for manufacturing a thermoplastic resin container according to claim 1, characterized in that the above-mentioned blend resin is used.