JP4548588B2 - Molds and molded products - Google Patents

Description

The present invention relates to a technique for manufacturing a metal and plastic processing mold.

For the purpose of reducing the production cost and production period of a mold, a composite reinforced resin is often used as a material for a simple mold for metal and plastic processing (so-called simple mold).
Among these, the following materials are generally used for the simple mold for injection molding with the most severe molding pressure and temperature, and for the simple mold for press working which requires a very large compressive stress.
1: Epoxy resin or urethane resin with a large amount of inorganic materials such as aluminum and nickel blended and strengthened 2: ABS resin, thermoplastic resin with a large amount of inorganic materials such as aluminum and nickel blended and strengthened

As a processing method of the material, there are 1, cutting from a block 2, direct modeling using a layered modeling method (RP method) 3, and a reversal type in which a master model is cast-reversed.
These materials and processing methods are properly used according to the purpose.
In recent years, the development of 3D solid modeling technology has facilitated the conversion from product data to mold machining data 1, cutting resin molds using ultra-high-speed cutting technology 2, rapid tooling using RP method (modeling mold) I am scared.
Resin molds with ultra-high-speed cutting that are particularly easy to handle have a cutting speed faster than cutting of iron, aluminum, and low-melting alloys. The shape can be easily cut, and because of its light weight, it is easy to handle.

However, in the case of a resin material mold, the thermal conductivity is significantly inferior to that of metal, so that the material is required to have strict heat resistance as well as mechanical durability and dimensional stability.
In this regard, conventional epoxy and urethane materials are inferior in basic physical properties of the raw material (matrix material), so they cannot be used as mold materials as they are, and they are reinforced in large quantities (in many cases 50% or more by weight). Mixing fillers for use, but by adding a large amount of reinforcing fillers, cutting workability (cutting speed and durability of the cutting tool) is greatly impaired and the original mold processing cost and construction period are reduced. There is little reduction effect.
Also, the molds that are made cannot withstand the temperature gradient and are cracked, and they are vulnerable to repeated large mechanical loads, which is very problematic in terms of durability.
For this reason, it is only used as a part for trial manufactures centering on general purpose resin.

The object of the present invention is to suppress the blending of fillers as much as possible, while being able to process while maintaining sufficient machinability, for high temperature and high pressure repeated load during injection molding and large repeated compression load during press processing, The object of the present invention is to provide a molding die that can maintain sufficient rigidity, dimensional stability, and durability, and can also mold high-performance resins such as engineering plastics.

A material based on cast polyamide resin (so-called monomer cast nylon) with high crystallinity by polymerization of ω-lactam monomer using anionic polymerization is polymerized into a block shape, and this is used for processing such as high-speed cutting. Use as mold material.

The present invention is a plate-shaped cutting characterized in that it contains an ε-caprolactam polymer having a high degree of crystallinity obtained by blending various catalysts and polymerization initiators into ε-caprolactam to cause an anionic polymerization reaction and curing. These are a mold for molding obtained by cutting a mold material plate for processing, and a plastic injection molded product or a press-processed product processed by using the mold.

The same material is injected with ω / lactam represented by ε / caprolactam, which is heated and liquefied in a mold as is known, and polymerized using a polymerization initiator such as an anionic polymerization catalyst, tolylene diisocyanate, and the resin block is create.
In general, this is cut and used as a necessary product.
High crystallization rate than the material obtained by the water polymerization polyamide resin (so-called nylon 6) (about 50% crystallinity by X-ray diffractometry), uniform crystal structure (alpha form monoclinic) As a result, it has lower moisture absorption than so-called 6 nylon and has excellent heat resistance, wear resistance, and self-lubricating properties, and is used for durable parts such as wheels, gears, cams and bearings.

The present inventor noticed that the above-mentioned material is not only excellent in the above-mentioned characteristics but also rich in elasticity even in a high temperature region, and has excellent resilience against elastic deformation, such as high-temperature and high-pressure conditions such as injection molding. It was found that even if the deformation occurs temporarily below, the region within the elastic deformation is restored in the initial stage of the cooling process in which pressure is applied relatively uniformly, and an accurate shape can be transferred.
As a result, it has been found that a technical idea that can produce a simple mold having a balance between excellent machinability, durability against heat and pressure, and dimensional stability is established.

In the present invention, the ε · caprolactam polymer is an arbitrary polymer produced using ε · caprolactam as a main raw material. Examples thereof include polyamide 6 which is a homopolymer of ε · caprolactam, a copolymer of ε · caprolactam and another monomer, or a mixture thereof.

As the anionic polymerization catalyst used in the present invention, all compounds used in known alkali polymerization methods for lactams can be used.
That is, alkali metals, alkaline earth metals, hydroxides thereof, hydrides, carbonates, alkylates, alkoxides, Grignard compounds sodium naphthalene, and the like can be given.
Moreover, also about a polymerization initiator, all the compounds used for the well-known alkali polymerization method of lactams can be used. That is, organic isocyanate, acid chloride, ester, urea derivative, carbodiimide and the like can be mentioned.

An example of this invention is shown.
As a raw material adjustment, 1 to 50 parts by weight as a polymerization catalyst, preferably 2 to 10 parts by weight as sodium hydroxide and a co-catalyst adjusted as appropriate between 1 and 2 parts by weight, preferably 100 parts by weight of ε-caprolactam A tolylene diisocyanate prepared in a timely manner between 2 to 3 parts by weight is prepared.

The necessary amount of ε · caprolactam is heated in a container, preferably 100 ° C. to 200 ° C., more preferably 120 ° C. to 130 ° C., and liquefied, and the air in the container is replaced with nitrogen.
The polymerization catalyst and co-catalyst prepared in the liquid are added and poured into a predetermined mold while stirring, and the temperature is in the range of 100 ° C. to 160 ° C., preferably 130 ° C. to 150 ° C., preferably 10 minutes to 120 minutes, preferably Annealing is performed for 60 to 120 minutes to complete the polymerization reaction, and after cooling, the molded body is taken out.
The crystallinity of the ε · caprolactam polymer is preferably as high as possible, and is adjusted as needed according to the above conditions. The crystallinity required in the present invention is not particularly limited, but if it exceeds 60%, the toughness decreases. Since there is a fear, it is preferable to make it lower.
Specifically, it is adjusted to 37% to 75%, preferably 50% to 60% as measured by X-ray diffraction measurement.

In order to increase the crystallization rate of the material in the present invention, it is preferable to blend a crystal nucleus material necessary for uniformly controlling the fork crystal growth size and ensuring stable characteristics.
The crystal nucleus material is not particularly limited, but inorganic fine particles such as talc, mica, clay, silica and graphite, metal oxides such as magnesium oxide, aluminum oxide, iron oxide, zinc oxide and copper oxide, metal salts, nylon 6T, nylon 66 high melting point polyamide and the like.
The compounding ratio of the crystal nucleating agent is 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, based on 100 parts of the ε · caprolactam polymer.

The shaped material used in the present invention has a high degree of crystallinity, so it has a high elastic modulus, extremely little deformation under high resin pressure (within elastic deformation), low linear expansion coefficient, and dimensional stability without using fillers. Can be secured. In spite of having a fork polyamide structure, the water absorption is low in the standard state and the dimensions of the molded product are stable.
However, as long as it has a polyamide structure, the influence of strength and dimensional changes due to slight moisture absorption is inevitable. For this reason, it is preferable to mix some reinforcing fillers for the purpose of reinforcing mechanical strength and durability, reducing linear expansion coefficient, and improving water absorption.
However, as with other resin molds, large fillers such as glass fibers have an adverse effect on the surface finish, so fine fillers with a finely finished surface state are used. The blending of the fine filler added in the present invention is adjusted at a weight ratio of 10% to 40%, preferably 10% to 20%, in order to maintain the machinability (free machining). In the present invention, because of the characteristics of the matrix material, the purpose of blending the reinforcing filler can be sufficiently achieved even at a low blending ratio compared to other resin molds.
In this example, 20% by weight of fine whiskers made of aluminum borate was used as a fine inorganic filler during polymerization. The fine filler in the present invention is not particularly limited, and examples thereof include calcium carbonate, titanium oxide whisker, wollastonite, kaolin, graphite, carbon black, clay, and glass balloon.

In addition, in order to improve lubricity and releasability as mold applications, solid lubricants such as graphite and molybdenum disulfide, and polymer powders such as polytetrafluoroethylene should be added in a few parts to several tens of parts by weight. Is preferred.

The shape of the fine filler in the present invention is not particularly limited, but is preferably fine particles having a particle diameter of about 10 nm to 50 μm, or fine fibers having a length of about 1 μm to 50 μm and a diameter of about 10 nm to 5 μm, more preferably a particle diameter of 10 nm. Ultrafine particles of about 10 μm or so, or ultrafine fibers having a length of about 1 μm to 30 μm and a diameter of about 10 nm to 1 μm are used.
In particular, a so-called nanocomposite using acicular and layered ultrafine fillers functions not only as a reinforcing function but also as a crystal nucleating agent, and a great effect can be obtained with a small amount of blending.

The member formed into a plate shape is cut with tool steel, and the target mold shape is dug. For the cutting process, a normal milling machine or lathe can be used regardless of the shape, and a cutting tool such as an end mill can be sufficiently processed with a normal plastic processing tool.
The present inventor has been able to produce a resin mold in which only a product portion is processed at high speed without requiring special equipment and processes such as a carbide tool and electric discharge machining necessary for ordinary mold production.

Further, in the present invention, in order to reduce the influence of moisture absorption, it is desirable to perform a uniform humidification process in advance in the shape of the shaped material and maintain a moisture content of about 0.5 to 1% by weight before cutting. However, since an excessive moisture content causes a decrease in elastic modulus, the moisture content must be suppressed to 1% or less by weight. The polyamide resin shape material in the present invention is stable at a moisture content of about 1% in the air in the standard state, and there is no particular inconvenience in storage, but it is stored in a dry state in order to further stabilize the size and strength. It is preferable to perform drying before use.

Usually, the resin mold has a very poor thermal conductivity, so the mold temperature often rises above the allowable temperature in continuous molding. As a result, dimensional stability cannot be maintained, and the molded product cannot be cooled sufficiently. There are inconveniences such as failure to withstand temperature gradient strain and die breakage. In order to prevent this, in order to cool the mold, a very long molding cycle time must be secured in the injection molding.
In the case of this embodiment as well, there remains a problem in mass productivity even if the mechanical, thermal strength and durability of the mold can be maintained.

Since the present invention is mainly composed of a polyamide resin having a large water absorption, it is not preferable to pass cooling water for cooling the mold. Also, it is not preferable to drill holes for cooling from the viewpoint of maintaining strength.

Therefore, in the present invention, as shown in FIG. 1, for mold cooling, a thin cooling rod made of aluminum or copper is embedded in the resin mold from the mold base side around the portion that needs to be cooled, and is closely attached to the mold base provided with cooling piping. With the function of a heat pipe. As a result, an efficient mold cooling system could be easily constructed without impairing the mechanical strength of the resin mold.
The cooling system is not limited to the example of the present invention, but is effective for an injection mold, a press mold, a vacuum mold, and a blow mold using other resin materials.

After finishing the produced mold, it is assembled into the mold base.
The inventor molded polypropylene, ABS (acrylic, butadiene, styrene copolymer) resin, polyacetal resin, etc. in the shape as shown in FIG. 2 using the injection mold produced as described above. Checked dimensions. Table 1 shows the results.
As shown in Table 1, when the injection pressure is 600 kgf / cm2 or less, the dimensional stability does not change at all and the dimensional stability as the mold design dimensions is shown, and the same dimensional stability is maintained in the molding of the polyacetal resin. It was confirmed that continuous molding over 5000 shots was possible.

Another feature of the present invention is that the molding surface is relatively soft because there is no filler compounding or is suppressed as much as possible. It can be done.
Thereby, ceramic insert molding, which has been difficult in the past, can be easily performed.

The present invention enables high-speed cutting of complex shapes easily, and maintains dimensional stability while withstanding high-temperature, high-pressure resin molding loads that are tough and continuous, despite the fact that it is a resin mold that is inexpensive, fast delivery, and lightweight. It is possible to carry out molding processing, and it is possible to obtain an ideal resin mold with extremely higher durability than other resins, even if it is not a conventional specialist. It can be widely used for applications where initial investment is difficult due to economic reasons such as low-volume, multi-product production and trial production.

In addition, the present invention can be applied not only to cutting processing but also to the production of inverted molds using a product model manufactured from gypsum, resin, etc. using a polymerization process in the atmosphere as a master, and a variety of mold manufacturing methods It can be applied to.

The resin mold according to the present invention is not only used for injection molding, but also for molding a plastic material that needs to be molded by applying temperature and pressure, such as vacuum and pressure molding, as well as for pressing a metal sheet that is relatively easy to plastically process such as aluminum and magnesium. It can also be used as a mold, and can be applied to the above-mentioned use of a small variety of products that are difficult to make the initial investment.

Mold cross section Molded product shape and measurement dimensions

Explanation of symbols

1 Mold base (metal)
2 Cooling piping (refrigerant)
3 Resin mold part 4 Cooling rod

Claims (2)

A mold for plastic injection molding processing or a metal, characterized in that it is composed of a resin shape material containing monomer cast nylon, which is a polymer of W-lactam monomers utilizing anionic polymerization. Mold for pressing plastic plates. Plastic injection mold characterized by comprising a resin shape material in which fine filler is added to monomer cast nylon, which is a polymer of W-lactam monomer using anionic polymerization, or for metal, press working Type.

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