JP2007169468A - Plastic molded article and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a plastic molded article reducing environmental loads and simultaneously having excellent impact resistance and heat resistance at a low cost. <P>SOLUTION: This plastic molded article 1 having sites 2 to which dynamic loads are added, when assembled or used, is characterized by using a biomass raw material resin as a main material and more enhancing the resin crystallization degrees of the dynamic load-added sites 2 than the resin crystallization degrees of other sites. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plastic molded product whose main material is a resin derived from a biomass raw material, and a method for producing the same. Specifically, the present invention relates to a part that is mechanically loaded when assembled into a product, and a mechanical load that is used during use. The present invention relates to a plastic molded product that requires impact resistance strength and a manufacturing method thereof.

Conventionally, a huge amount of plastic products have been used, but the waste causes serious global environmental problems such as landscape obstruction to nature, threats to living things, and environmental pollution.
Conventionally used resins derived from petroleum raw materials include, for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and the like, and these disposal methods include incineration and landfilling.

However, conventional disposal methods have various problems. For example, in incineration, since resins such as polyethylene, polypropylene, and polystyrene have high combustion calories, it has been a problem that the incinerator is easily damaged.
Polyvinyl chloride has a relatively low calorie calorie, but generates harmful gas during incineration and may cause air pollution.
As for landfilling, the conventional resin derived from petroleum raw materials has high chemical stability, so it remains semipermanently while remaining in its original form, and environmental pollution and the shortage of the landfill site itself become serious. There was a problem such as.

As mentioned above, when plastics that have been widely used in the past are discarded in the natural environment, they are scientifically stable and thus lose their aesthetics over a long period of time. However, the impact on biological resources is getting worse.
In recent years, research on biodegradable polymers has been conducted in order to solve such problems.
Examples of biodegradable plastics that have been studied for practical use include aliphatic polyesters, modified PVA (polyvinyl alcohol), cellulose ester compounds, modified starches, and blends thereof.
In particular, among aliphatic polyesters, polylactic acid polymers are attracting attention as semisynthetic polymers.

Resin derived from biomass raw materials mainly made from plants is a material that can effectively reduce the environmental impact in that it uses almost no petroleum as a raw material.
Among resins derived from biomass raw materials, in particular, polylactic acid has attracted attention as a constituent material of a molded body because it has excellent biodegradability (see, for example, Patent Document 1 below).

However, resins derived from biomass raw materials generally have a problem that they are inferior to plastics conventionally used in general in terms of physical properties, such as low mechanical strength and low heat resistance.
As specific physical properties, the melting point and glass transition temperature are low, the crystallization temperature located in the middle is low, and the crystallization rate is low. For example, polylactic acid has a melting point of about 170 ° C, a crystallization temperature of about 110 ° C, and a glass transition temperature of about 57 ° C. Will hardly crystallize. Therefore, although it is a crystalline polymer, the heat resistance of the molded product is equal to or lower than the glass transition temperature, and it has been necessary to improve it as a practical resin.

The impact strength and heat resistance temperature are improved by promoting the crystallization of the resin derived from the biomass raw material. As a technology for promoting this crystallization, a crystallization nucleating agent is added to the resin derived from the biomass raw material. (For example, refer to Patent Documents 2 to 4 below.)
Also, a method of annealing treatment to promote crystallization of the molded product (for example, see Patent Document 5 below), a method of promoting crystallization in a mold (for example, see Patent Documents 6 and 7 below), etc. There is.

JP 2005-74791 A Japanese Patent No. 335964 Japanese Patent No. 3334338 Japanese Patent No. 2688330 JP-A-8-73628 JP 2005-74791 A JP 2005-138458 A

However, in the method of adding a crystallization nucleating agent to the above-described resin, if the crystallization nucleating agent is added excessively in order to increase the crystallization speed, the molded product becomes brittle or a sink is generated on the surface of the molded product. It is easy to cause troubles such as.
Further, the method of promoting the crystallization of the entire molded product by annealing treatment tends to cause a problem that the molded product shrinks unevenly or the molded product is deformed by releasing the molding distortion.
Furthermore, the method for promoting the crystallization of the entire molded product in the mold has a long resin occupying time in the process, resulting in a problem of cost increase due to an increase in molding time. In view of such a problem, when trying to release a molded product without securing a sufficient molding time, the mold temperature is usually higher than the glass transition temperature of the resin, so that crystallization is insufficient (amorphous state). The troublesome part becomes soft state and deforms at the time of mold release.

  Therefore, in the present invention, in order to solve the above-described problems of the prior art, a molded article using a biomass raw material resin having a practically sufficient impact strength and heat resistance without a long molding time. And a manufacturing method thereof.

  In the present invention, at least at the time of assembly or use, it is a plastic molded product having a part to which a mechanical load is applied, the main material is a biomass raw material resin, and the resin crystallinity constituting the part to which the mechanical load is applied However, the present invention provides a plastic molded article having a higher crystallinity than that of other parts.

  According to a second aspect of the present invention, there is provided the plastic molded product according to the first aspect, wherein the portion to which the mechanical load is applied is a screw mounting portion.

  According to a third aspect of the present invention, there is provided the plastic molded product according to the first aspect, wherein the portion to which the mechanical load is applied is a protrusion at the time of assembly.

  According to a fourth aspect of the present invention, there is provided the plastic molded product according to the first aspect, wherein the portion to which the mechanical load is applied is a snap fit portion.

  According to a fifth aspect of the present invention, there is provided the plastic molded product according to the first aspect, wherein the portion to which the mechanical load is applied is a positioning portion at the time of assembly.

  In the invention of claim 6, when the resin crystallinity of the material constituting the portion to which the mechanical load is applied is 1.0 when the state in which the biomass raw material resin to be used is completely crystallized is 1.0, A plastic molded article according to any one of claims 1 to 5 is provided.

  The invention according to claim 7 provides the plastic molded article according to any one of claims 1 to 6, wherein the biomass raw material resin is a blend of a biodegradable resin and a petroleum raw material resin.

  According to an eighth aspect of the present invention, there is provided a plastic molded article in which a crystallization nucleating agent is contained in the biomass raw material resin in order to increase the resin crystallinity.

  The invention according to claim 9 is a method for producing a plastic molded article having a portion to which a mechanical load is applied at least during assembly or use, wherein a biomass raw material resin is used as a main material, and the biomass is produced using a mold. A step of molding a raw material resin, and the temperature of a mold for creating a portion to which the mechanical load is applied is set in a range of −10 ° C. to + 40 ° C. based on the crystallization temperature of the biomass raw material resin. A method for producing a plastic molded product is provided in which the temperature of a mold for creating other parts is set to be equal to or lower than the glass transition temperature of the biomass raw material resin.

  The invention according to claim 10 is a method for producing a plastic molded article having a portion to which a mechanical load is applied at least during assembly or use, wherein the biomass raw material resin is used as a main material, and the biomass is produced using a mold. A step of molding the raw material resin, a step of taking out from the mold, and heating only the portion where the mechanical load is applied within a range of −10 ° C. to + 40 ° C. based on the crystallization temperature of the biomass raw material resin, Provided is a method for producing a plastic molded article having a process for improving the process.

In invention of Claim 11, it is a manufacturing method of the plastic molded product which has a site | part which requires a mechanical load at the time of an assembly | attachment or use at least, Comprising: The biomass raw material resin is used as a main material, The said biomass is used using a metal mold | die. It shall have a process of molding raw material resin,
Provided is a method for producing a plastic molded product, wherein the mold shrinkage rate of a mold for creating a mechanically loaded portion is set to be larger than the mold shrinkage rate of a mold for creating other portions.

  In a plastic molded product that includes a part that is mechanically loaded during assembly or use, a biomass raw material resin is used as the main material of the molded product, and the part that includes the mechanically loaded part is more than other parts. By making the resin crystallinity high, it was possible to obtain a plastic molded article having low cost and excellent durability while reducing the environmental burden (claims 1 to 5).

  By making the degree of crystallinity of the part where the mechanical load is applied into 1.0 when the state in which the biomass raw material resin used is completely crystallized is 1.0, various durable consumer goods can be obtained. A plastic molded product derived from a biomass material having usable impact strength and heat resistance temperature could be provided at a low cost (Claim 6).

  By making the biomass raw material resin a blend of biomass raw material resin and petroleum raw material resin, not only the parts where mechanical load is applied, but also the impact strength and heat resistance temperature of the entire molded product are raised, and further the mechanical load is increased. Thus, a plastic molded product derived from a biomass raw material having improved impact strength and heat-resistant temperature can be provided.

  By including a crystallization nucleating agent that increases the crystallization speed in the biomass raw material resin, the crystallization speed of the resin can be increased, the molding time can be shortened, and the crystallinity of the mechanically loaded portion can be reduced at a low cost. It was possible to provide a plastic molded article derived from a biomass material having enhanced impact strength and heat resistance temperature (claim 8).

  The temperature of the mold for creating the mechanically loaded portion is within the range of -10 ° C to + 40 ° C based on the crystallization temperature of the biomass raw material resin used, and the temperature of the mold for creating other portions is , Biomass that is lower than the glass transition temperature of the biomass raw material resin to be used, thereby increasing the crystallinity of the part where mechanical load is applied without increasing the molding time and increasing the impact strength and heat resistance temperature. A plastic molded product derived from a raw material could be produced at low cost (claim 9).

  After the plastic molded product is taken out from the mold after molding, only the part where the mechanical load is applied is heated to a range of −10 ° C. to + 40 ° C. based on the crystallization temperature of the biomass raw material resin to be used. By increasing the degree of crystallization, the occupancy time of the mold can be shortened, the crystallinity of the part where mechanical load is applied at low cost can be increased, and it is derived from the biomass raw material having high impact strength and heat resistance temperature. A plastic molded product could be provided (claim 10).

  Even if the degree of crystallinity of the molded product varies depending on the part by setting the molding shrinkage rate of the mold that creates the mechanically loaded part to be larger than the molding shrinkage percentage of the mold that creates the other part. Thus, a plastic molded product derived from a biomass raw material with high accuracy was obtained, which could be produced with the shape accuracy (dimension) as intended.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following examples.
The plastic molded article of the present invention has at least a part to which a mechanical load is applied at the time of assembly or use, the main material is a biomass raw material resin, and the material constituting the part to which the mechanical load is applied is: The resin crystallinity is higher than that of the material constituting the other part.

  The present invention can be applied to any conventionally known plastic molded product, and a portion where a mechanical load is applied refers to a load exerted by a predetermined portion exhibiting mechanical and physical functions. This means a receiving part, and specifically includes a screw attachment part, a protrusion part when assembled with other members, a snap fit part, a positioning part when assembled, and the like.

Regarding the material constituting the above-described mechanically loaded portion, the degree of crystallinity of the resin is preferably 0.8 or more when the state in which the biomass raw material resin to be used is completely crystallized is 1.0. . Thereby, the impact resistance strength and heat resistance of this part can be sufficiently enhanced in practice.
In order to increase the resin crystallinity, a crystallization nucleating agent may be appropriately contained.

The biomass raw material resin used in the plastic molded article of the present invention may be a blend obtained by mixing a conventionally known petroleum raw material resin with a biodegradable resin.
Thereby, the mechanical strength and physical properties of a biodegradable resin generally having low strength and poor heat resistance can be improved.

Next, the manufacturing method of the plastic molded product of this invention is demonstrated.
Biomass raw material resin is used as the main material, and resin molding is performed using a mold. At this time, the temperature of the mold that creates the mechanical load of the target plastic molded product is determined by the biomass raw material resin crystal. The temperature of the metal mold | die which creates other site | parts is set to below the glass transition temperature of biomass raw material resin, setting to the range of -10 degreeC-+40 degreeC on the basis of chemicalization temperature.

In addition, the step of increasing the crystallization of the portion where the mechanical load is applied may be performed separately from the injection molding step.
In other words, only the part where the mechanical load is taken out from the injection mold is heated in the range of −10 ° C. to + 40 ° C. based on the crystallization temperature of the biomass raw material resin, and a process for increasing the crystallization is separately performed. May be.

  Moreover, it is preferable to set the mold shrinkage rate of a mold for creating a mechanically loaded portion of a plastic molded product to be larger than the mold shrinkage rate of a mold for creating other portions.

[Example 1]
FIG. 1 shows a schematic view of a cover which is one of exterior parts used for a copying machine and a printer.
FIG. 1A is a side view, and FIG. 1B is a plan view.
FIG. 2 shows a schematic cross-sectional view of the state where the cover 1 is assembled.
The cover 1 is provided with four projections 2 for assembly. When the cover 1 is attached to the lower cover 3, the cover 1 is assembled in the state shown in FIG. The same applies when the cover 1 is removed from the lower cover 3.

As a material of the cover 1, a blend body in which polylactic acid derived from a biodegradable resin raw material and polycarbonate derived from a petroleum raw material were mixed at a ratio of 60:40 was used.
Polylactic acid has a melting point of about 170 ° C., a crystallization temperature of about 110 ° C. and a glass transition temperature of about 57 ° C., and polycarbonate has a melting point of about 220 ° C. and a glass transition temperature of about 145 ° C.
Furthermore, appropriate amounts of various additives such as flame retardants, antioxidants, plasticizers, compatibilizers, and crystallization nucleating agents were added.

As the material for the lower cover 3, ABS resin derived from petroleum raw materials was used.
However, the present invention is not limited to this, and resins derived from other petroleum raw materials and biomass raw materials can be used.

FIG. 3 shows a schematic configuration diagram of an injection mold for producing the plastic molded product of the present invention.
It has a cavity 7 surrounded by a pair of insertion pieces 6 that form a part including a projection for assembling a pair of cavity pieces 5a and 5b forming a cavity surface.
The entrance piece 6 is provided with a cartridge heater 8 and a thermocouple 9, and the cartridge heater 8 and the thermocouple 9 are connected to a temperature control device (not shown) prepared outside the mold.
Further, a heat insulating member 10 is provided between the cavity pieces 5 a and 5 b and the entrance piece 6.
Further, the mold base 11 is provided with a water pipe 12 for heating and cooling the entire mold, and is connected to an aqueous medium temperature control device (not shown) provided outside the mold.
In addition, conventionally well-known various ceramics, a thermosetting resin, etc. are applicable to the heat insulation member 10. FIG.

The plastic molded product of this example was produced as follows.
The injection mold 30 is set in a predetermined injection molding machine (not shown), and the cover 1 shown in FIGS. 1 and 2 is molded.
The cylinder temperature is 220 ° C., the temperature of the entire mold is set to 30 ° C. which is lower than the glass transition temperature of polylactic acid, and the cartridge heater 8 provided in the entrance frame 6 is set to 120 ° C. which is higher than the crystallization temperature of polylactic acid. did.
After the cavity 7 is filled with molten resin and a resin pressure is generated in the cavity 7, the resin is cooled and solidified for 3 minutes, and then the inside of the mold is used with a predetermined molded product take-out device (not shown). And cooled at room temperature.
Thereby, the plastic molded product of the present invention was produced.

[Comparative Example 1]
A schematic cross-sectional view of the injection mold 13 used in this example is shown in FIG.
The molded product was the same cover 1 as in Example 1 above, and the raw material resin was also the same as in Example 1 above.
The injection mold 13 has a cavity 15 surrounded by a pair of cavity pieces 14a and 14b that form a cavity surface.
The mold base 16 is provided with a cartridge heater 17 and a thermocouple 18, and the cartridge heater 17 and the thermocouple 18 are connected to a predetermined temperature control device (not shown) outside the mold.

The plastic molded product in this example was produced as follows.
The injection mold 40 is set in a predetermined injection molding machine (not shown), and the cover 1 is molded.
The cylinder temperature was set to 220 ° C., and the mold temperature was set to 120 ° C., which is higher than the crystallization temperature of polylactic acid.
After the cavity 15 is filled with molten resin and a resin pressure is generated in the cavity 15, the resin is sufficiently crystallized over 30 minutes, and then gold is used using a predetermined molded product take-out device (not shown). The mold was removed and cooled at room temperature.

[Comparative Example 2]
The molded product was the same cover 1 as in Comparative Example 1, and the same material resin, injection mold and molding equipment as those in Comparative Example 1 were used.
The injection mold 40 is set in a predetermined injection molding machine (not shown), and the cover 1 is molded.
The cylinder temperature was set to 220 ° C., and the mold temperature was set to 30 ° C. below the glass transition temperature of polylactic acid.
After the cavities 14a and 14b were filled with molten resin and a resin pressure was generated in the cavities, the resin was cooled and solidified for 3 minutes. Then, it removed from the metal mold | die using the predetermined molded article taking-out apparatus (not shown), and cooled at room temperature.

Next, the correlation between the density and the degree of crystallinity was examined using the samples of the plastic molded products produced in Example 1 and Comparative Examples 1 and 2 described above.
Density measurement is performed on the protrusions of the molded products produced in Example 1, Comparative Example 1 and Comparative Example 2, and the density of the molded product in Comparative Example 1 is set to 1 and the density of the molded product in Comparative Example 2 is set to 0. The crystallinity of Example 1 was calculated to be 0.83.

Next, when the molded product (cover 1) produced in Example 1 and Comparative Example 2 was assembled to the lower cover 3, the molded product of Example 1 could be assembled without causing cracks or breakage. . This is because the molded article of Example 1 was produced so that the crystallinity of the protrusion 2 which is a part where a mechanical load is applied during assembly and removal is higher than that of the other parts, and thus has excellent impact strength. It was possible to secure a practically high function.
On the other hand, in the molded product of Comparative Example 2, cracks occurred in the protrusions 2 during assembly or removal. The molded product of Comparative Example 2 is not manufactured so that the projecting portion 2 of the cover 1, that is, the resin crystallinity of the portion to which a mechanical load is applied during assembly or removal is higher than the crystallinity of other portions. Therefore, the impact strength is inferior, and the function in practical use cannot be sufficiently secured.

  As described above, the plastic molded article of the present invention can have high impact strength by a simple molding process by controlling the crystallinity according to the function of the part.

[Example 2]
The molded product in this example is the same cover 1 as in Comparative Example 1, and the same material resin, injection mold, and molding equipment as those in Comparative Example 1 are used.
The injection mold 40 was set in a predetermined injection molding machine (not shown), and the cover 1 was molded.
The cylinder temperature was set to 220 ° C., and the mold temperature was set to 30 ° C. below the glass transition temperature of polylactic acid.
After the cavities 14a and 14b were filled with molten resin and a resin pressure was generated in the cavities, the resin was cooled and solidified for 1 minute.
Then, it removed from the metal mold | die using the predetermined molded article taking-out apparatus (not shown), and also cooled at room temperature.
Next, the heating jig 50 shown in the schematic sectional view of FIG. 5 was prepared. As described above, the molded product (cover 1) taken out from the mold and cooled is set on the heating jig 50 so that the protrusions 2 come into contact with each other. Next, the heating jig 50 was heated to 120 ° C., which is higher than the crystallization temperature of polylactic acid, and held for 30 minutes to increase the crystallinity. Then, it cooled to room temperature and took out the molded article from the heating jig 50.
In this example, a plastic molded product was produced by dividing the injection molding step and the subsequent crystallization enhancement step into two steps.
By setting it as such a process, the time for resin to occupy the inside of a metal mold | die can be shortened, and when there are many manufacturing lines especially, the cost reduction as a whole can be aimed at.

The resin used in the above-described examples is a blend of polylactic acid and polycarbonate, but the present invention is not limited to these examples.
For example, a resin derived from a biomass raw material is not particularly limited as long as it is a resin manufactured using raw materials extracted from plants or microorganisms without using petroleum as a raw material. In addition to polylactic acid, polyglycolic acid, Polycaproic acid, and a copolymer raw material resin such as polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polyethylene adipate, a copolymer (polybutylene succinate adipate) combining these resins, Saccharide polymers such as cellulose derivatives, starch, chitin and chitosan can be used.
In addition to polycarbonate, various resin materials such as polymethyl methacrylate, polystyrene, ABS resin, AS resin, polyethylene, and polypropylene can be used as the petroleum raw material resin to be blended.
These blending ratios are not limited to 60:40.
Even when the blending ratio is selected appropriately and petroleum raw material resin is not included, the impact strength is increased and the heat resistance is improved by increasing the crystallinity of the part where mechanical load is applied to other parts. The effect was obtained.

In the first and second embodiments described above, the part to which the mechanical load of the plastic molded product is applied is the assembling protrusion, but the present invention is not limited to these examples.
For example, there are screw mounting parts (holes for screws or tapping screw insertion parts), positioning parts when assembling a snap fit, and these are all mechanical loads when assembling or using plastic molded products. By forming such a part so that the degree of crystallinity of the resin is higher than that of other parts, an effect of improving impact strength and heat resistance can be obtained.

(A) The schematic side view of the cover which is one of the exterior components used for a copying machine or a printer is shown. (B) The schematic plan view of the cover which is one of the exterior parts used for a copying machine or a printer is shown. The schematic sectional drawing in the state where the cover was assembled is shown. The schematic block diagram of the injection mold is shown. The schematic block diagram of the injection mold used in the comparative example is shown. The schematic sectional drawing of a heating jig is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cover 2 Protrusion part 3 Lower cover 5a, 5b Cavity piece 6 Entering piece 7 Cavity 8 Cartridge heater 9 Thermocouple 10 Heat insulation member 11 Mold base 12 Water pipe 14a, 14b Cavity piece 15 Cavity 16 Mold base 17 Cartridge heater 18 Thermocouple 19 Heating jig 20 Cartridge heater 21 Thermocouple 22 Heat insulation member 30 Injection mold 40 Injection mold 50 Heating jig

Claims (11)

A plastic molded article having a part to which a mechanical load is applied at least during assembly or use,
Biomass raw material resin is used as the main material,
A plastic molded product characterized in that the crystallinity of the resin constituting the part to which the mechanical load is applied is higher than the crystallinity of the resin in other parts.   The plastic molded article according to claim 1, wherein the portion to which the mechanical load is applied is a screw attachment portion.   The plastic molded article according to claim 1, wherein the part to which the mechanical load is applied is a protrusion at the time of assembly.   The plastic molded article according to claim 1, wherein the portion to which the mechanical load is applied is a snap fit portion.   The plastic molded article according to claim 1, wherein the part to which the mechanical load is applied is a positioning part at the time of assembly.   The resin crystallinity degree of the material constituting the portion to which the mechanical load is applied is 0.8 or more when a state in which the biomass raw material resin to be used is completely crystallized is 1.0. Item 6. A plastic molded article according to any one of Items 1 to 5.   The plastic molded product according to any one of claims 1 to 6, wherein the biomass raw material resin is a blend of a biodegradable resin and a petroleum raw material resin.   The plastic molded article according to any one of claims 1 to 7, wherein the biomass raw material resin contains a crystallization nucleating agent that increases the degree of crystallinity of the resin. A method for producing a plastic molded article having a portion to which a mechanical load is applied at least during assembly or use,
Using a biomass raw material resin as a main material, and having a step of molding the biomass raw material resin using a mold,
The temperature of the mold for creating the part to which the mechanical load is applied is set in a range of −10 ° C. to + 40 ° C. based on the crystallization temperature of the biomass raw material resin,
A method for producing a plastic molded product, characterized in that a temperature of a mold for creating another part is set to be equal to or lower than a glass transition temperature of the biomass raw material resin. At least a method for producing a plastic molded article having a part to which a mechanical load is applied during assembly or use,
Using biomass raw material resin as the main material,
Molding the biomass raw material resin using a mold;
Removing from the mold;
Production of a plastic molded product comprising a step of heating only a portion to which the mechanical load is applied within a range of −10 ° C. to + 40 ° C. based on a crystallization temperature of the biomass raw material resin to increase crystallization. Method. At least a method for producing a plastic molded article having a part to which a mechanical load is applied during assembly or use,
Using a biomass raw material resin as a main material, and having a step of molding the biomass raw material resin using a mold,
A method for producing a plastic molded product, characterized in that a molding shrinkage rate of a mold for creating a part to which a mechanical load is applied is set larger than a molding shrinkage rate of a mold for creating another part.

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