JPH0771818B2 - Manufacturing method of resin press-molded product with grain - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a press-formed product obtained by subjecting a molten resin sheet to embossing, for example, an embossed resin press-formed product such as a vehicle interior plate. The present invention can be understood as an applied patent of Japanese Patent No. 1278242 (Japanese Patent Publication No. 59-23691) provided by the applicant.

Conventional technology Conventionally, the surface of a resin sheet extruded from a die is embossed with a molding roll, and then vacuum molding or pressure molding is applied to bring the back surface of the resin sheet, which has not been embossed, into close contact with a mold to give a product. Methods of making shapes are known. This prior art is the most general molding method for textured products, but it is not suitable for deep-drawing products and large products, and the molding time is very long and the cost is high, and the applicable range is extremely limited.

In this prior art example, there is no teaching regarding a series of techniques for subjecting the present invention to forming a sheet of a molten resin into a sheet, and forming and press-forming the sheet.

Generally, large-sized draw-molded products that are not suitable for injection molding, vacuum molding, etc. and glass-fiber resin molded products that are difficult to inject depend on compression molding by applying a mechanical press. A resin press-molded product is one in which a resin sheet stocked by a manufacturer is reheated to form a softened sheet, which is then charged into a mold and press-molded to shape it as a product. The method of heating and press-forming has poor fluidity, and it is particularly difficult to form fine and three-dimensional textures on the surface of a vertical wall or the like.

Problems to be Solved by the Invention As described above, in the prior art, it is not possible to recognize any disclosure about a specific method of forming a sheet of molten resin into a sheet and embossing and press-molding in a series of steps.

In the case of the embossing by the press molding, uniform and beautiful embossing cannot be expected, and wrinkles may be generated or a defective embossing product may be produced.

In addition, in the method of forming the grain by press molding, it is unavoidable that the physical property deterioration due to reheating of the base material, cracks and rough skin due to this are inevitable, and there is a loss of heat energy to reheat the sheet that has been preliminarily heated. This imposes an economic burden on the electricity consumption, etc., and also deteriorates productivity.

Further, as in the former example, in the method of forming the product as a product by adhering the back surface of the high melting point resin sheet, which is not grain-formed, to the mold by applying vacuum forming or pressure forming, as described above, deep drawing It is not suitable for large-sized products and the molding time is very long and the cost is high, and its application range is extremely limited.

In view of the above circumstances and problems, the present invention has been made in consideration of integrated production of resin sheet molding, embossing, and press molding.

Means for Solving the Problems As a means for solving the problems, the present invention uses two or more kinds of mixed resins as a resin base material and melts them into a sheet, and the resin sheet has the highest melting point in the mixed resin. The surface of the sheet is subjected to embossing by adjusting the temperature above the melting point of the resin component, and in the subsequent press molding, the temperature drop point is from the melting point of the lowest melting point resin in the maximum specific heat range to the freezing point (crystallization peak temperature). ) Around, and preferably press-molding while performing temperature control (temperature control) so as to maintain the temperature range, and press-molding, so as to form the product as a product while maintaining good crimp molding. It was done.

As a suitable example of the resin base material, a mixed resin containing a polypropylene resin as the highest melting point resin component and a polyethylene resin as the lowest melting point resin component is shown.

Further, as the temperature control when the press machine is charged, the temperature of the embossed resin sheet is controlled by radiant heat from both sides of the sheet so as to maintain it in the temperature falling range near the freezing point from the melting point of the lowest melting point resin component, and after the temperature control. , A method of charging into a molding die is provided.

Action The present invention forms the mixed resin into a sheet as described above, and appropriately press-forms the same while subjecting it to press molding at a predetermined temperature lowering point. That is, in the present invention, attention is paid to the fact that when the temperature of the mixed resin drops, solidification (crystallization) begins at a temperature lowering point lower than the melting point of the resin having the lowest melting point, such as natural cooling without solidifying the embossed resin sheet as it is. The temperature lowering range in which the resin sheet temperature is near the freezing point from the melting point of the resin having the lowest melting point in the mixed resin is selected while promoting the temperature lowering, and the resin sheet is charged into the molding die and press-molded.

According to the present invention, press molding can be performed at a melting point of the highest melting point resin, that is, a temperature sufficiently lower than the embossing molding temperature, and a very beautiful embossed resin press molding without causing defects such as attenuation of wrinkles and generation of wrinkles. Goods can be provided, and in addition, press molding can be performed at an appropriate molding temperature, and sound shaping can be performed without impairing the physical properties of the resin sheet.

Further, the mixed resin having a difference in melting point shows maximum specific heat near the freezing point lower than the melting point of the resin having the lowest melting point at the time of temperature decrease, and is most stable in terms of temperature, and it is difficult to cool. Therefore, by capturing this range and putting it in the mold and performing press molding, it is possible to shape the resin sheet soundly without a rapid temperature drop due to cooling of the mold, and especially when the sheet surface is overheated. It is possible to effectively prevent the occurrence of cracks, skin roughening, etc. upon cooling, and to produce a high-quality wrinkled resin press-formed product that does not impair the wrinkle molding state formed at the time of forming a resin sheet.

Further, when the resin sheet is charged into the press mold, the temperature of the resin sheet is controlled by radiant heat from both sides of the embossed resin sheet to maintain the above temperature range, thereby preventing variations in mold temperature. Effectively preventing grain damage and erasing due to temperature control, and at the same time, soaking the resin sheet, which is the molding base, on the surface and the core of the resin sheet, effectively preventing molding defects due to temperature unevenness.

Embodiments Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

In the present invention, two or more kinds of mixed resins having sufficiently different melting points are used as the base material of the resin sheet. In view of the case where the mixed resin is three or more types, the resin component having the highest melting point by contrast is also called the highest melting point resin component even when it is two types, and the resin component having the lowest melting point by contrast is the lowest melting point resin component. Call.

The above-mentioned mixed resin is heated and melted at a temperature equal to or higher than the melting point of the resin having the highest melting point, extruded from the die 1 as shown in FIG. 1, and the extruded molten resin is sandwiched between the sheet forming rolls 2 and 3 for surface forming and thickness. Sheets are formed while taking out. One of the sheet forming rolls 2 and 3, that is, the roll 3 is a texture forming roll,
While the resin sheet is being formed, the surface of the sheet is embossed with the embossing roll 3.

The sheet forming rolls 2 and 3 are further functioned as a temperature control roll, and the resin sheet is wound around the rolls 2 and 3 and the sheet PS
In the predetermined temperature control process TC ₁ , the temperature is controlled so that the temperature is maintained at the melting point of the highest melting point resin or higher, and the embossing is performed.

Explaining a suitable example of the above sheet forming and embossing roll, as shown in the figure, the back surface of the molten resin extruded from the die 1 is changed from near the top dead center of the roll 2 to approximately a quarter arc surface near the side dead center. Along with the crossing, the surface of the molten resin is brought into contact with the surface of the molten resin at the side dead center, and the sheet is pressed between the rolls 2 and 3 to perform the embossing. While keeping the surface contact, the forming roll 3 is crossed from the side dead center to a position past the bottom dead center to ensure a sufficient embossing process and promote the embossing. FIG. 4 shows an enlarged cross-sectional view of the embossed resin sheet having the embossed E thus formed.

As an example of the composition of the mixed resin, an example of mixing a polypropylene resin component and a polyethylene resin component will be given. Polypropylene resin has a melting point of around 170 ° C, and polyethylene resin has a melting point of around 130 ° C, with the former being the highest melting point resin and the latter being the lowest melting point resin. Both resins are compatible with each other and have a sufficient difference in melting point.

When the polypropylene resin is a mixed resin of polyethylene resin, for example, in the range of 170 ° to 200 ° C., for example, a resin sheet is formed by melting at 200 ° C., and 170 ° C. or more by the sheet forming / texturing forming rolls 2 and 3, for example, the highest melting point. The embossing is performed near a temperature drop of 190 ° C, which is higher than the melting point of the resin.

In addition to the above as composition examples of two kinds of mixed resins, polyamide
An example is a mixed resin having compatibility with 66 (melting point 250 ° C.) and polyamide 6 (melting point 215 ° C.).

Further, as a composition example of a mixed resin of three or more kinds, a mixture example of polypropylene resin, polyethylene resin and ethylene vinyl acetate resin (melting point 70 ° C to 97 ° C), or a mixture example of polyamide 66, polyamide 6 and polyamide 12 (melting point 178 ° C). Indicates. Both composition examples show the case where three kinds of resins are compatible with each other, and according to the above, polypropylene resin or polyamide 66
The above three kinds of mixed resin are melted at a melting point equal to or higher than, and embossed.

The resin sheet PS that has been embossed as described above is supplied to the cutting unit 6 via the guide roll 4 and the pinch roll 5 and cut into unit lengths.

Next, the unit embossed resin sheet PS 'is transferred to the conveyor 7,8
At that time, it is conveyed to the press device 10, and during this time, the temperature is urged to drop, and within a predetermined temperature falling range, it is put into the lower mold 11 and immediately the upper mold 12
Is lowered to perform press molding. A suitable sheet feeder, for example, a vacuum feeder 14 is used for charging the lower mold 11.

Then, the temperature near the freezing point is selected from the melting point of the resin having the lowest melting point in the mixed resin as the temperature lowering range, and the mold is charged.

That is, in the above composition example, in the mixed resin of polypropylene resin and polyethylene resin, the above-mentioned mold is charged in a temperature lowering range from a melting point of polyethylene resin having a low melting point of 130 ° C. to a freezing point of 125 ° C.,
Press molding is performed to shape the product.

Generally, two or more kinds of mixed resins having different melting points have a characteristic of starting solidification (crystallization) at a temperature lower than the melting point of the lowest melting point resin when the temperature is lowered, and exhibit maximum specific heat in the vicinity of the solidifying point from the melting point. In other words, having the maximum amount of heat and being in the coldest and most hateful state,
It also exhibits appropriate surface rigidity and stable heat retention, satisfying the optimum conditions for press molding.

The same applies to other composition examples, for example, even in the case of the mixed resin of the polypropylene resin, the polyethylene resin, and the ethylene vinyl acetate resin, the melting point of the ethylene vinyl acetate resin, which is the lowest melting point resin, starts to solidify at a temperature lower than 70 ° C. The solidification point is captured, the mold is introduced, and press molding is performed to shape the object.

In press molding, it is indispensable to put a resin sheet in a mold and clamp the mold, and natural cooling during this period, in particular, supercooling at a contact surface with a lower mold remarkably impairs moldability. The present invention solves this problem as much as possible by setting the above conditions.

In order to ensure the above temperature conditions, as shown in FIG. 1 and FIG. 2, the temperature control furnace 9 is arranged on the loading side to the press device 10, and the unit embossed resin sheet PS ′ cut at the cutting section 6 is While being introduced into the temperature control furnace 9 by the conveyor 7 and being transported in the furnace,
In the temperature adjustment process TC ₂ , the temperature of the unit embossed resin sheet PS ′ is adjusted so that it falls within the above set temperature range.

As the most preferable temperature control method, as shown in the drawing, the infrared heating device 15 is installed in a non-contact state so as to face the front surface and the back surface of the unit embossed resin sheet PS ′, and the unit embossed resin sheet PS ′ is radiated by the infrared heating device 15. Heat from both sides.

For example, in the case of the mixed resin of the polypropylene resin and the polyethylene resin, the unit embossed resin sheet PS 'is heated and kept at a temperature of about 125 ° C. by the radiant heat.

In this case, at least the introduction conveyor 7 uses a perforated belt having a large number of ventilation holes. Further, the outlet conveyor 8 has one end in the furnace, receives the unit embossed resin sheet PS 'in the furnace, carries it out of the furnace, and the other end is extended to the side of the press machine arranged at the furnace outlet, The temperature-regulated unit-textured resin sheet PS'is supplied to the press machine at a higher speed by speed switching.

As described above, the extrusion of the molten resin, the band-shaped sheet forming, the embossing, and the press molding are carried out consistently to continuously produce the embossed resin press-formed product having a beautiful embossing.

EFFECTS OF THE INVENTION As described above, according to the present invention, by using the melting point of the resin having the highest melting point of the resin sheet of the mixed resin, proper embossing can be achieved, and the heat retaining state of the resin sheet at the time of temperature decrease is used Appropriate press molding can be performed in the completed state of molding, and mixed resin can be rationalized in integrated production by forming a resin sheet into a resin sheet, embossing, and embossing a resin sheet.

That is, the present invention provides the above-mentioned mixed resin into a sheet, which is subjected to press molding at a predetermined temperature lowering point while appropriately performing the embossing, and when the temperature of the mixed resin is lowered, the melting point of the resin having the lowest melting point is used. Focusing on solidification (crystallization) starting at a lower temperature drop point, the resin sheet temperature is the lowest melting point resin content in the mixed resin while promoting the temperature decrease accompanied by natural cooling without solidifying the embossed resin sheet. A temperature-falling range from the melting point to the vicinity of the freezing point is selected, and the mixture is put into a molding die and press-molded to obtain a resin press-molded product with a grain.

According to the present invention, press molding can be performed at a melting point of the highest melting point resin, that is, a temperature sufficiently lower than the embossing molding temperature, and a very beautiful embossed resin press molding without causing defects such as attenuation of wrinkles and generation of wrinkles. A product can be provided, and in addition, press molding can be performed at an appropriate molding temperature, and sound shaping can be performed on the embossed resin sheet without impairing the physical properties of the resin sheet.

Further, the mixed resin having a difference in melting point exhibits maximum specific heat near the freezing point lower than the melting point of the resin having the lowest melting point when the temperature is lowered, and is most stable in terms of temperature and cooled. Therefore, by capturing this range, charging the mold, and performing press molding, the embossed resin sheet can be shaped soundly without a rapid temperature drop due to cooling of the mold, and in particular, with the mold. It is possible to effectively prevent the contact surface of the sheet from being overcooled to cause cracking, skin roughening, and the like, and it is possible to produce a high-quality embossed resin press-formed product that does not impair the embossed molding state when the resin sheet is formed.

Further, when the embossed resin sheet is charged into the press mold, the temperature of the embossed resin sheet is controlled by radiant heat from both sides of the resin sheet to maintain the above temperature range, whereby variations in the mold mold temperature can be prevented. In addition, the damage and erasure of the grain due to the temperature control are effectively prevented, and at the same time, the resin sheet as the molding base is soaked on the surface and the core portion to effectively prevent the molding defect due to the temperature unevenness.

[Brief description of drawings]

FIG. 1 is a side view schematically showing an apparatus for producing a resin press-formed product with a grain for explaining an embodiment of the present invention, FIG. 2 is a plan view of the same, and FIG. FIG. 4 is an enlarged sectional view of the embossed resin sheet. 1 ... Die, 2, 3 ... Sheet forming / texture forming roll (temperature control roll), 9 ... Heating furnace, TC ₁ , TC ₂ ... Temperature control process, 10
…… Pressing device, 11 …… Lower mold, 12 …… Upper mold, PS …… Resin sheet, PS ′ …… Unit embossed resin sheet, E …… Emboss.

Claims (3)

[Claims] 1. A molten resin is formed into a sheet by melting two or more kinds of mixed resins, and the resin sheet is subjected to temperature control at a temperature equal to or higher than the melting point of the highest melting point resin component in the mixed resin, and the surface of the sheet is subjected to emboss molding.
The embossed resin press molding is characterized in that the embossed resin sheet is charged into a molding die in a temperature lowering range near the freezing point from the melting point of the resin having the lowest melting point in the mixed resin, and press molding is performed to shape the product as a product. Manufacturing method of goods. 2. The embossed resin press-formed product according to claim 1, wherein the mixed resin contains a polypropylene resin as the highest melting point resin component and a polyethylene resin as the lowest melting point resin component, respectively. Manufacturing method. 3. The embossed resin sheet is temperature-controlled from both sides of the sheet by radiant heat so as to be maintained in a temperature-falling range near the freezing point from the melting point of the resin having the lowest melting point, and after the temperature-control, it is charged into a molding die. The method for producing a resin press-formed product with a grain according to claim 1, wherein the method is performed.