JPH0717816B2 - Shape memory resin vacuum molded product manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has the characteristic of restoring the shape of an original molded product by appropriately deforming it in a heated state, cooling it, and then bringing it back into the heated state again. The present invention relates to a method for manufacturing a given shape memory resin vacuum molded product.

[Prior Art] Bolinorbornene is a polymer obtained by ring-opening polymerization of norbornene, and its glass transition point is 35 ° C, which is slightly higher than room temperature. It is known that the original molded article can be restored to its original shape by cooling it to room temperature, using it, and then heating it to a temperature above the glass transition point, for example, 40 ° C. As the molding method, the weight average molecular weight of polynorbornene is about 20.
Since it is very high at more than 0,000, ordinary plastic molding is difficult, and compression molding is applied.

The inventors previously found that by mixing polyethylene into polynorbornene, it was possible to obtain a shape memory composition having good processability that can be applied to a general molding method, and applied for a patent.

A molded product can be obtained from this composition by a pressure molding method, but in the press molding method, pressure molding takes time to give good shape memory, productivity is low, and cost is high. Is not preferable.

[Problems to be Solved by the Invention] If a shape-memory molded product is obtained by a vacuum molding method, productivity is high and preferable, but in order to impart sufficient shape-memory property of the molded product, the shape is retained for a long time. It was considered necessary to apply the thermal history under the condition. The inventors
The present inventors have completed the present invention by finding out that it is sufficient to heat a vacuum-molded shape to a high temperature for a certain period of time by repeating research on obtaining a shape memory property in a relatively short time by the vacuum-molding method.

[Means for Solving the Problems] Thus, according to the present invention, a composition containing polynorbornene containing a heat stabilizer and polyethylene is formed into a sheet of 0.1 mm to 5 mm, and the sheet is softened by heating to form a vacuum forming machine. In the range of 130 to 210 ° C., which is higher than the heating and softening temperature by 5 ° C. or more in a state where the molded product is attached to a mold.
A method for producing a shape-memory resin vacuum-molded product is provided, which comprises heating and holding for 15 to 80 seconds, then cooling and taking out from a mold.

In other words, after vacuum forming, by heating and holding at a temperature higher than the heating temperature by 5 ° C. or more in a state of being attached to the mold for a certain period of time, the shape memory property is efficiently imparted in a short time. . Examples of the polynorbornene used in the present invention include CDF Chymy (Cdf Ch
ime), which has an average molecular weight of 2,000,000 or more, a true specific gravity of 0.96, a glass transition point of 35 ° C., and a particle size of 0.3 to 0.
It is a white powder of 4 mm.

Polyethyne is added to the polynorbornene. Polyethylene improves processability, but if the amount of polyethylene added is large, the shape memory property of the product is deteriorated. Therefore, the amount added may be selected in consideration of the memory property.

Further, a heat stabilizer is added because it is exposed to a high temperature during processing, and as the heat stabilizer, those usually used for plastics molding processing, for example, a phenol-based or phosphite-based heat stabilizer are used.

Antioxidants, lubricants, fillers, colorants and the like usually used for resin processing may be appropriately added to the above mixture in order to enhance moldability, impart decorative properties to products, impart rigidity to products, and the like. .

As a method for forming a vacuum forming sheet, a method of forming the above mixture into a sheet by calendering and pressing,
A method in which a sheet is extruded by an extruder is applied, and a sheet having a thickness of about 0.1 mm to 5.0 mm is prepared for vacuum forming.

The sheet is then cut into a size suitable for a vacuum molding machine mold and heated on the mold for the molding operation. Since the glass transition temperature of polynorbornene is 35 ° C., this heating may be performed at an appropriate temperature above this temperature, but in consideration of moldability and the like, practically, it is about 120 to 170 ° C. and 20 to 60 ° C.
Heated on the mold for a second. Then, the air between the mold and the sheet is vacuum-sucked and molded.

The thus vacuum-formed product is kept for 20 to 80 seconds within the temperature range of 130 to 210 ° C. at a temperature 5 ° C. or more higher than the heating temperature before the vacuum forming, with the mold attached. , Imparts shape memory. As for the heating temperature for adding shape memory, shape memory can be obtained even before heating by vacuum forming, but for that reason the holding time becomes very long and the shape memory becomes insufficient. 5 ° C
It is necessary to raise the temperature above. It should be noted that a difference of 30 ° C is sufficient, and a temperature of more than 30 ° C may cause thermal deterioration. It is preferable to impart the shape memory property in the range of 130 to 210 ° C. If the temperature is 130 ° C or lower for 20 seconds or less, molding failure or the state before molding returns, and the shape memory property of the product becomes insufficient. Further, heating at 210 ° C. or higher or for 80 seconds or longer causes thermal deterioration, which may cause surface roughening and holes at the corners of the mold. Therefore, within the range of the above temperature and time, the heating temperature before forming, the thickness of the sheet, etc. are taken into consideration for selection.

After the shape-memory property-imparting operation in this manner, the molded product is cooled to a room temperature of 35 ° C. or lower, which is the glass transition temperature of polynorbornene, by spray cooling with water, blowing cold air, or the like, and taken out from the mold.

[Working] The product obtained as described above has a glass transition temperature of polynorbornene of 35 ° C or higher, for example, in warm air of 40 ° C or higher, or in hot water, bent into an appropriate shape, or flattened. Deformation is fixed by cooling it to room temperature in this deformed state. When it is desired to return to the original shape again, it can be restored to the original shape of the molded product by immersing it in hot water and bringing it to a temperature above the glass transition temperature.

[Examples] The present invention will be specifically described with reference to Examples below.

Polynorbornene (CdF, France, trade name Nosolex, degree of polymerization 200 or more, particle size 0.3 to 0.4 mm) was used.

To 90 parts by weight of polynorbornene, 10 parts by weight of low-density polyethylene and 4 parts by weight of phenolic heat stabilizer were added,
Roll kneading was performed for 20 minutes, and a sheet having a thickness of about 1 mm was formed.
This product was transferred to a press molding machine and heated at 150 ° C for 15 minutes at a pressure of 10
It was pressed at 0 kg / cm ² to make a smooth glossy sheet with a thickness of 1.0 mm.

Next, this sheet was transferred onto a mold, subjected to heat-softening treatment at 150 ° C. for 45 seconds, and then vacuum-formed under a vacuum of 600 mmHg.
Next, the molded product was attached to the mold and held at 170 ° C. for 30 seconds to give shape memory property. afterwards,
The product was taken out from the mold and cooled to a room temperature of 25 ° C., which was lower than the glass transition temperature of polynorbornene, by blowing cold air.
As the mold, a rectangular tray having a length of 16 cm, a width of 9 cm and a depth of 2 cm and a child's toy'face 'having a width of about 15 cm and a length of about 20 cm were used.

The obtained product had a beautiful skin, and the product corresponding to the mold accurately was obtained.

The above two types of products were immersed in warm water of 40 ° C., folded or squeezed, and then cooled to room temperature to fix the deformed shape. When the deformed one is immersed again in 40 ° C warm water, it is restored to the same shape as the original tray, 'face',
It could be cooled and fixed in its original shape.

For comparison, after being vacuum-formed, a sheet which was kept at a sheet heating temperature of 150 ° C. for 20 seconds had a very bad shape as a molded article and was unsuitable as a product.

[Effects of the Invention] According to the present invention, it becomes possible to efficiently produce a shape memory product by vacuum forming, which has been conventionally difficult to achieve in view of shape memory in terms of productivity, and can efficiently produce trays such as tableware and children. It will open a wide range of applications to industrial toys, various daily necessities that utilize changes in shape, and industrial products.

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Claims (1)

[Claims] 1. A composition of polynorbornene containing a heat stabilizer and polyethylene is formed into a sheet having a thickness of 0.1 mm to 5 mm, the sheet is softened by heating and formed by a vacuum forming machine, and the formed product is subsequently formed into a mold. A shape-memory resin vacuum-molded product characterized by being heated and held at a temperature of 130 ° C to 210 ° C for 15 to 80 seconds higher than the above-mentioned heat-softening temperature in an adhered state, then cooled and taken out from a mold. Law.