JPH02274526A - Method for manufacturing shape memory resin molded body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a shape memory resin molded article, and more specifically, a method for producing a synthetic resin molded article having a shape that is difficult to remove from a mold with good workability. Relating to a method of manufacturing.

[Prior art] There are known methods of molding polynorbornene resins, boron 1/tan resins, and other molded products using liquid raw materials in a mold by reaction injection molding (RIM), resin transfer molding, etc. There is. In these molding methods, a convex mold (core) and a concave mold (cavity) are used in combination, and a liquid raw material is supplied to the space in the middle to perform molding. For example, polyurethane molding using the RIM method using incyanate and polyol as reaction components (liquid raw materials) requires significantly lower injection pressure than normal injection molding of thermoplastic resins, so it cannot be used in inexpensive and lightweight molds. ,
Furthermore, since the raw material has good fluidity within the mold, it is possible to produce large molded bodies or molded bodies with complicated shapes.

However, depending on the shape of the molded product, demolding may be difficult. For example, in the case of a molded article having a U-shaped cross section, the molded article is in close contact with either a concave mold or a convex mold, and cannot be easily removed from the mold. Alternatively, it is difficult to demold a molded article such that a concave mold covers a convex mold. Therefore, when manufacturing molded objects with shapes that are difficult to demold, a mold with a core structure containing inserts is used, which requires setting the inserts and cleaning after molding. However, the operation is complicated and the workability is poor, and the mold is expensive, so it is uneconomical. It is also conceivable to produce a molded article with a shape that is easy to demold and then perform secondary shaping to produce a molded article with a predetermined shape, but it is difficult to accurately secondary shape the molded article into a predetermined shape.

[Problem to be solved by the invention]

An object of the present invention is to efficiently obtain a molded product having a shape that is difficult to demold with simple operations.

As a result of intensive studies to solve the problems of the prior art, the present inventors discovered that after molding a cross-linked resin with shape memory into a predetermined shape that is difficult to demold in a mold, The molded product is deformed and demolded at a temperature above the heat deformation temperature, and then restored to its original shape by heating above the restoring temperature, so it is a molded product with a shape that is difficult to demold using normal molding methods. The inventors have discovered that molding can be performed with good workability even if there is such a material, and have completed the present invention based on this knowledge.

[Means for Solving the Problems 1] Thus, according to the present invention, in a method for manufacturing a synthetic resin molded article having a shape that is difficult to remove from a mold, a crosslinked resin having shape memory properties is used as the synthetic resin, and the After molding a resin into a molded body of a predetermined shape that is difficult to demold in a mold, the molded body is deformed and demolded at a temperature higher than the heat deformation temperature of the resin, and then heated to a temperature higher than the restoring temperature. A method for producing a shape memory resin molded article is provided, which is characterized in that it is restored to its original predetermined shape.

The present invention will be explained in detail below.

(Shape-memory resin) The synthetic resin used in the present invention is a crosslinked resin having shape-memory properties. By being a crosslinked type, a molded article having excellent mechanical strength, heat resistance, etc. can be obtained.

Specific examples of crosslinked shape memory resins include polyurethane resins, epoxy resins, polyester resins, and ring-opening polymers of norbornene monomers (polynorbornene resins).
etc. can be mentioned.

The polynorbornene resin used in the present invention is a resin obtained by bulk ring-opening polymerization of a norbornene monomer in a mold in the presence of a metathesis catalyst system. Examples of norbornene monomers include bicyclics such as dicyclopentadiene and dihydrodicyclopentadiene, tetracyclics such as tetracyclododecene, bicyclics such as tricyclopentadiene, and heptacyclics such as tetracyclopentadiene. , their alkyl substituted products (e.g., methyl, ethyl, propyl, butyl substituted products, etc.), alkylidene substituted products (e.g., ethylidene substituted products, etc.), aryl substituted products (e.g., phenyl, tolyl substituted products, etc.), etc. are preferable. . In addition, the polynorbornene resin used in the present invention needs to be crosslinked, and for this purpose a small amount (10% by weight or more, preferably 30% by weight or more) of crosslinkable monomers is used in the total monomers. Here, the crosslinkable monomer is a polycyclic norbornene monomer having two or more reactive double bonds, and specific examples thereof include dicyclopentadiene, tricyclopentadiene, and tetracyclopentadiene. Therefore, if the norbornene monomer and the crosslinking monomer used are the same, there is no need to use any other crosslinking monomer. A ring cycloolefin or the like may be used in combination.

The crosslinked resin used in the present invention usually has a glass transition temperature (Tg) of 60°C or higher, preferably 60 to 250°C, and must have enough strength to not break when demolded after molding. is necessary.

In addition, these crosslinked resins contain antioxidants, plasticizers,
Various additives such as fillers, fiber reinforcements, pigments, colorants, and impact modifiers such as elastomers may be included.

These cross-linked resins have shape memory properties, and can plastically deform a molded object of one shape into a molded object of another shape and fix that shape by cooling, and can also be used at temperatures above the restoring temperature. , it can be restored to its original shape by reheating.

Among these crosslinked resins, polynorbornene resins and polyurethane resins are preferred. In particular, polynorbornene resins are suitable as resins for molded articles in fields where heat resistance is required, since polymers having a Tg of 150° C. or higher are easily available.

(Mold removal method) The crosslinked resin is molded in a mold by RIM method, casting molding method, resin transfer molding method, etc., but in the present invention, it has a shape that is difficult to demold in the mold. Targets molded objects. Shapes that are difficult to demold are not particularly limited, but include, for example, cylindrical containers with a bottom, containers with small openings, various molded objects with shapes that cover a concave mold and a convex mold, etc. I can do it.

After molding, the molded body is demolded by applying an external force to the molded body at a temperature higher than the heat deformation temperature of the crosslinked resin to deform it into a shape that is easy to demold. The demolded molded product retains its deformed shape when cooled, but when reheated to a temperature higher than the restoring temperature of the crosslinked resin, its shape memory property restores the molded product to its original shape that is difficult to demold. These points will be explained with reference to the drawings.

Figure 1 (A) shows a molded article with a cross-sectional opening shape in a convex mold (
2) and a concave mold (1) for molding in combination, it is a schematic cross-sectional view of a mold and a molded body.

Normally, when molding such a container-shaped molded article, the opening of the container is widened and the container is tapered so that it becomes narrower toward the convex tip so that it can be easily demolded (although this method In some cases, a molded article having a shape without a taper as shown in FIG. 1(A) is required.

However, after molding, when the molded body is cooled, the convex mold (2) and the concave mold (1) in FIG. 1(A) are removed, and the molded body is taken out, the molded body is It sticks tightly to one of the molds and cannot be easily removed from the mold.

Therefore, when the molded body is in close contact with the convex mold (2), the molded body is heated to a temperature higher than the heat deformation temperature of the crosslinked resin, as shown in Fig. 1 (B), and the molded body is heated in the direction of the arrow. By applying an external force to the mold, the mold is deformed to widen the opening and released from the mold. The demolded molded body retains its deformed shape as it cools, but when reheated to a temperature above the restoring temperature of the crosslinked resin, it restores to its original shape as shown in Figure 1 (C). . Further, when the molded body is brought into close contact with a concave mold, the molded body may be heated and deformed so as to narrow the opening of the molded body, and then removed from the mold.

FIG. 2(A) is a diagram illustrating an example of molding a molded article in a shape such that a concave mold (11) covers a convex mold (12), and usually the insert (14, 15) A mold with a core structure is used. After molding, the concave mold (11) and inserts (14, 15) are removed to take out the molded product.
The work of removing the nest, especially the work of removing the nest (14), is difficult and time consuming. Therefore, as shown in Figure 2 (B),
If the molded body is heated above the heat deformation temperature, deformed by applying an external force in the direction of the arrow, and after demolding, the deformed molded body is reheated above the restoring temperature, as shown in Figure 2 (C). , it can be restored to its original shape. Although FIG. 2 shows an example using a moss and a nest, if this method is adopted, a molded article having a shape that is difficult to demold can be easily obtained without using a nest.

To heat the molded product to a temperature higher than the heat distortion temperature of the crosslinked resin or higher than the restoration temperature, appropriate means such as air heating using an oven, hot plaster heat gun, etc., steam heating, heating in a heated liquid, etc. are adopted. be able to.

The restoration temperature is within a temperature range of not less than the heat distortion temperature of the crosslinked resin and not more than 1 degree of decomposition, preferably 10 degrees Celsius or more than the heat distortion temperature,
Preferably, the temperature is higher than 30°C. The heating time during restoration depends on the size, deformation state, heating temperature, etc. of the molded object, but is usually from several seconds to several tens of minutes, preferably about 1 to 200
That's about it.

In addition, when the molded object is a structural material such as a bonding material or a construction fixing material, it may be constructed in a deformed state and then restored.

〔Example〕

The present invention will be explained below by giving specific examples.
It should be noted that the present invention is not limited to these examples.
In the following examples, parts and % unless otherwise specified.
are based on weight.

[Example 1] As a reaction stock solution, 70% dicyclopentadiene and cyclopentadiene trimer (80% asymmetrical and 20% symmetrical) were used.
% mixture) Liquids A and B having the following composition and having a mixture of 30% as a monomer component were mixed in a 1=1 ratio and used.

Solution A: ■ Monomer component ■ Phenolic antioxidant (Irganox 259 manufactured by Ciba Geigy) 2% ■ Diethyl aluminum chloride 40 mmol concentration ■ n-propatool 44 mmol concentration ■ Silicon tetrachloride 20 mmol concentration B1 night; ■ Monomer component ■ Libdate on tri(tridecyl)ammonium 10 milliliters of liquid A and liquid B were each sent to a power mixer at a volume ratio of 1:1 using a gear pump, and then the convex shape shown in Figure 1 (A) was transferred. Mold (2) and concave mold (
1), outer diameter 106mm, inner diameter 100mm,
The mixture was immediately poured into a mold having a cylindrical space with a bottom and a height of 200 mm. The mold temperature was 70°C. The injection time was about 10 seconds, and the reaction was carried out in the mold for 3 minutes.

These series of operations were performed under a nitrogen atmosphere.

After the molded body was cooled, the two molds were separated, and the molded body was brought into close contact with the convex mold (2).

Therefore, the molded body (3) was heated with a hot gun to a temperature approximately 30°C higher than the heat distortion temperature (160°C),
An external force was applied using a copper wedge-shaped jig in the direction shown by the arrow in Figure 1(B), and the molded body was deformed in the direction of widening the opening. The deformed molded body could be easily demolded. After demolding, the molded body was air-cooled to maintain its deformed state, but when it was heated again to about 200°C with a hot gun,
The molded object was restored to its original shape as remembered. It should be noted that the molded product did not break or crack during deformation, and did not show any strain in its shape (exhibiting good shape restorability).

(The following is a blank space) [Effects of the Invention] According to the present invention, a molded article that is difficult to demold can be demolded from a mold by heating and deforming it using a crosslinked resin having shape memory properties as a synthetic resin, and then It can be manufactured efficiently with a simple operation of restoring it using shape memory properties.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic cross-sectional views showing the process of demolding a molded article that is difficult to demold from a mold and restoring the molded article according to the manufacturing method of the present invention. t, it...Concave molds 2, 12...Convex molds 3, 13...Molded bodies 14, 15...Inserts

Claims (2)

[Claims] (1) In a method for manufacturing a synthetic resin molded article having a shape that is difficult to demold from a mold, a cross-linked resin having shape memory is used as the synthetic resin, and the resin is molded into a predetermined shape that is difficult to demold from the mold. A shape characterized in that, after being molded into a molded body, the molded body is deformed and demolded at a temperature higher than the heat deformation temperature of the resin, and then restored to its original predetermined shape by heating to a higher temperature than the restoring temperature. A method for producing a memory resin molded body. (2) A molded article obtained by the method according to claim 1.