JP2008239730A - Ultraviolet ray-cured foam and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet ray-cured foam which is good in flexibility, has high strength and is free from stickiness. <P>SOLUTION: This ultraviolet ray-cured foam is obtained by mechanically foaming an ultraviolet ray-curable resin raw material comprising an oligomer, a diluent, an ultraviolet ray polymerization initiator and a foam stabilizer by an Oakes mixer or the like and then curing the product with ultraviolet rays wherein the diluent comprises a monofunctional monomer having a highly reactive acrylamide group. The oligomer has an acrylate or methacrylate group at the terminal and a mol. wt. of 8,000 to 40,000. It is preferable that the amount of the monofunctional monomer having the acrylamide group is 20 to 40 pts.wt. per 100 pts.wt. of the total amount of the oligomer and the monomer. The ultraviolet ray-cured foam preferably has a density of 400 to 700 kg/m<SP>3</SP>, an elongation of 100 to 200%, and a tensile strength of 1.0 to 2.0 MPa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a shock-absorbing material such as a foot rubber for furniture and information equipment, and an ultraviolet curable foam suitable for applications requiring flexibility and strength.

  Conventionally, in order to stably install a precision instrument or the like on a desk, a floor or the like, a foot rubber may be attached to the precision instrument or the like. Polyurethane foam is used as the foot rubber. However, polyurethane foam has a problem that it takes a relatively long time to complete foam curing at the time of manufacture.

  On the other hand, as a foam that can shorten the curing time at the time of manufacture, there is an ultraviolet curable foam. The ultraviolet curable foam is a foam obtained by mechanically foaming an ultraviolet curable resin raw material containing an oligomer, a diluent, an ultraviolet polymerization initiator, and a foam stabilizer and curing the raw material with ultraviolet rays. Mechanical foaming is a method of foaming not by foaming with a foaming agent that generates foaming gas by decomposition of a compound or the like but by stirring using a mixer or the like.

  By the way, impact cushioning materials such as foot rubber are required to have flexibility and strength, but conventional ultraviolet-curing foams are difficult to satisfy both the flexibility and strength required for impact cushioning materials. It was. That is, in the ultraviolet curable foam, a bifunctional monomer is used as a diluent to increase the strength. However, the crosslinking density is high, the flexibility is poor, and the elongation is particularly inferior. Further, as a result of the lack of flexibility and poor elongation of conventional ultraviolet curable foams, handling properties when producing ultraviolet curable foams in the form of long sheets are poor. For example, ultraviolet curable foams can be used as scrolls during continuous production. In this case, there is a problem that the ultraviolet curable foam is easily broken.

  Furthermore, for the production of UV curable foams, a mechanically foamed (foamed) UV curable resin raw material is applied onto a plastic film, and the UV curable resin raw material on the plastic film is irradiated with UV light to generate UV light. There is a method in which a curable resin raw material is cured, and then an ultraviolet curable foam is peeled off from the plastic film. Further, there is also a method in which an ultraviolet curable resin raw material after foaming (foaming) is continuously applied onto a continuously supplied plastic film and cured by irradiation with ultraviolet rays.

  However, since the ultraviolet curable resin material applied on the plastic film is cured by being irradiated with ultraviolet rays in contact with oxygen in the air, the surface of the ultraviolet curable resin material is inhibited from polymerization by oxygen (so-called oxygen inhibition). ), The curability is poor, and the resulting foam is sticky with surface tackiness, which makes it difficult to handle as a product.

JP-A-6-287376 Japanese Patent Laid-Open No. 7-258978 JP 61-137711 A JP-A-3-54230 JP-A-9-174733

  This invention is made | formed in view of the said point, Comprising: The softness | flexibility and high intensity | strength ultraviolet curable foam and the manufacturing method which can manufacture the ultraviolet curable foam without stickiness are provided.

  The invention according to claim 1 is an ultraviolet curable foam obtained by mechanically foaming an ultraviolet curable resin material containing an oligomer, a diluent, an ultraviolet polymerization initiator, and a foam stabilizer, and then curing with ultraviolet rays. It consists of a monofunctional monomer having a group.

  The invention of claim 2 is characterized in that, in claim 1, the oligomer has an acrylate group or a methacrylate group at the terminal and has a molecular weight of 8,000 to 40,000.

The invention of claim 3 is characterized in that, in claim 1 or 2, the ultraviolet curable foam has a density of 400 to 700 kg / m ³ , an elongation of 100 to 200%, and a tensile strength of 1.0 to 2.0 MPa.

  According to the invention of claim 4, the ultraviolet curable resin raw material containing an oligomer, a diluent composed of a monofunctional monomer having an acrylamide group, an ultraviolet polymerization initiator and a foam stabilizer is mechanically foamed, and the foamed ultraviolet curable resin is foamed. The resin raw material is applied to at least one of the two plastic films having ultraviolet transparency, the other plastic film is laminated on the surface of the ultraviolet curable resin raw material, and the ultraviolet transparent plastic An ultraviolet curable foam characterized by curing the ultraviolet curable resin raw material by irradiating ultraviolet rays through a film to form an ultraviolet curable foam, and then peeling the two plastic films from the ultraviolet curable foam. Related to the manufacturing method.

  According to the ultraviolet curable foam of the present invention, in an ultraviolet curable foam obtained by mechanically foaming an ultraviolet curable resin raw material containing an oligomer, a diluent, an ultraviolet polymerization initiator, and a foam stabilizer, and then curing with ultraviolet rays, When the agent is composed of a monofunctional monomer having an acrylamide group, the foam has good flexibility and high strength, and can be made into a foam suitable as an impact buffering material.

  Further, according to the method for producing an ultraviolet curable foam of the present invention, an ultraviolet curable resin raw material including an oligomer, a diluent composed of a monofunctional monomer having an acrylamide group, an ultraviolet polymerization initiator, and a foam stabilizer is mechanically foamed. Then, at least one is sandwiched between two plastic films having ultraviolet transparency, and the ultraviolet curable resin raw material is cured by irradiating ultraviolet rays through the ultraviolet transparent plastic film to form an ultraviolet curable foam, Since the ultraviolet curable foam is produced by peeling the two plastic films from the ultraviolet curable foam, the surface of the ultraviolet curable resin material can be prevented from coming into contact with oxygen during the curing with ultraviolet rays. The surface of the resin material becomes sticky due to poor curability due to polymerization inhibition by oxygen (so-called oxygen inhibition). It can be prevented from becoming those sticky having. In addition, when the diluent is composed of a monofunctional monomer having an acrylamide group, an ultraviolet-curing foam having good flexibility and high strength can be obtained. Furthermore, since the ultraviolet curable resin raw material after foaming is cured in a state where both surfaces are covered with a plastic film, the obtained ultraviolet curable foam hardly causes a difference in shrinkage on both surfaces, and the quality is stabilized.

  Hereinafter, embodiments of the present invention will be described in detail. The ultraviolet curable foam of the present invention is obtained by mechanically foaming an ultraviolet curable resin raw material containing an oligomer, a diluent, an ultraviolet polymerization initiator, and a foam stabilizer and curing it with ultraviolet rays.

  As the oligomer, those having an acrylate group or a methacrylate group at the terminal and a linear portion made of polyurethane, epoxy, polyether, polyester, siloxane or the like are used. The molecular weight of the oligomer is preferably 8,000 to 40,000. By using such a high molecular weight oligomer, the elongation of the ultraviolet curable foam is improved. The oligomer can be produced by a method similar to a known prepolymer production method. For example, in the case of a urethane acrylate oligomer, it is produced from an aliphatic or alicyclic isocyanate, a polyol, and an acrylic ester monomer having an isocyanate group. Specifically, an isocyanate and an acrylate ester-based monomer having an isocyanate group are added to a tank heated to a predetermined temperature (for example, 80 ° C.) while stirring in a state where nitrogen is filled. It is carried out by adding a predetermined amount and reacting. Commercially available oligomers can also be used.

As the diluent, a monofunctional monomer having an acrylamide group [CH ₂ = CHCON] is used. By using a monofunctional monomer having a highly reactive acrylamide group, the flexibility of the ultraviolet curable foam can be improved and the strength can be increased. In addition, when an acrylate monomer with low reactivity is used, an unreacted part remains in the ultraviolet curable foam, causing a decrease in strength of the ultraviolet curable foam. The amount of the diluent composed of a monofunctional monomer having an acrylamide group is preferably 20 to 40 parts by weight in a total of 100 parts by weight of the oligomer and the diluent. When the amount is less than 20 parts by weight, the strength is lowered. On the other hand, when the amount is more than 40 parts by weight, the flexibility is deteriorated. Therefore, the range of 20 to 40 parts by weight is preferable for increasing the strength and improving the flexibility.

  The ultraviolet polymerization initiator is for initiating an oligomer polymerization reaction and generates free radicals by ultraviolet rays. As the ultraviolet polymerization initiator, hydroxyacetophenone-based, aminoacetophenone-based, acylacetophenone-based, oxime acetophenone-based, and the like can also be used.

  The foam stabilizer is one that stabilizes bubbles and refines bubbles during mechanical foaming, and includes a surfactant.

  In addition, an appropriate colorant and the like are included in the ultraviolet curable resin raw material. As the colorant, a colorant required for the ultraviolet curable foam is used. For example, when the ultraviolet curable foam is white, a white colorant is used.

The ultraviolet curable foam of the present invention has a density (based on JIS K 7222: 1999) of 400 to 700 kg / m ³ , an elongation (based on JIS K 6400) of 100 to 200%, and a tensile strength (based on JIS K 6400) of 1.0 to 2. 0.0 MPa is preferred. By setting the density, elongation and tensile strength in this range, it is possible to obtain an ultraviolet curable foam suitable as an impact buffering material such as a foot rubber. The elongation value is the flexibility of the ultraviolet curable foam, and the tensile strength value is a physical property value indicating the strength of the ultraviolet curable foam.

  FIG. 1 shows a manufacturing apparatus 10 for the ultraviolet curable foam. The manufacturing apparatus 10 includes a lower plastic film supply / winding means, an ultraviolet curable resin material mechanical foaming / coating means, an upper plastic film supply / winding means, an ultraviolet irradiation means, and an ultraviolet curable foam. And winding means.

  The lower plastic film supply / winding means rewinds the lower plastic film 11 from the lower plastic film supply roll 13 around which the lower plastic film 11 is wound, and supplies the lower plastic film 11 upward. After changing the direction in a substantially horizontal direction and supplying a predetermined distance, the direction is changed downward by a take-up lower roll 15, peeled off from the lower surface of an ultraviolet curable foam A described later, and taken up by a lower plastic film take-up roll 16. It is configured as follows.

  An ultraviolet curable resin raw material mechanical foaming / coating means is an ultraviolet curable resin after foaming (foaming) on the upper surface of the lower plastic film 11 supplied in a substantially horizontal direction in the vicinity of the supply-side lower roll 14. It is comprised with the mechanical foaming apparatus 21 which discharges the raw material P. FIG. The mechanical foaming device 21 includes various mixers such as an Oaks mixer, a Hobart mixer, and the like, which mixes and stirs an inert gas supplied from the outside with the ultraviolet curable resin raw material to foam (foam) the ultraviolet curable resin raw material. The foamed ultraviolet curable resin raw material P can be discharged onto the upper surface of the lower plastic film 11 supplied in a substantially horizontal direction. The mechanical foaming device 21 is capable of foaming (foaming) the ultraviolet curable resin raw material by stirring the gas into the ultraviolet curable resin raw material by stirring and discharging the foamed (foamed) state. If there is, it can be used without restriction. The inert gas is not particularly limited as long as it is in a gaseous state at normal temperature and pressure and does not deteriorate the ultraviolet curable resin. Examples thereof include inorganic gases such as carbon dioxide, nitrogen, argon, neon, and helium, and organic gases such as chlorofluorocarbons and low molecular weight hydrocarbons. Although the supply amount of the inert gas is appropriately determined, the supply amount in the case of nitrogen gas is preferably 1 to 10 L / min.

  The upper plastic film supply / winding means includes an upper plastic film supply roll 33 around which the upper plastic film 31 is wound, a knife coater 34, a winding side upper roll 35, and an upper plastic film winding roll 36. Is done.

  The upper plastic film supply roll 33 is provided above the lower plastic film supply / winding means. The upper plastic film 31 unwound from the upper plastic film supply roll 33 is supplied to the vicinity of the lower plastic film 11 supplied in a substantially horizontal direction, and is applied to the upper surface of the ultraviolet curable resin raw material P after foaming. Laminated.

  The knife coater 34 has a lower end in contact with the upper surface of the upper plastic film 31 laminated on the upper surface of the foamed ultraviolet curable resin raw material P, and changes the direction of the upper plastic film 31 to a substantially horizontal direction. The thickness of the ultraviolet curable resin raw material P after the foaming between the lower plastic film 11 and the upper plastic film 31 is adjusted. The distance between the lower end of the knife coater 34 and the lower plastic film 11 is substantially equal to the thickness of the target ultraviolet curable foam A. To be precise, the thickness of the ultraviolet curable foam A is made substantially equal to the value obtained by adding the thickness of the upper plastic film 31. Although the thickness of the ultraviolet curable resin raw material P after the foaming is set to an appropriate value, it is preferably 0.1 to 3.0 mm. By setting it within this range, ultraviolet rays are transmitted from one side to the opposite side of the ultraviolet curable resin raw material P after foaming during ultraviolet irradiation described later, and it becomes easy to obtain an ultraviolet curable foam A having a uniform cell distribution. That is, when the thickness is less than 0.1 mm, the influence of oxygen inhibition increases, and a sufficiently cured foam cannot be obtained. On the other hand, if it exceeds 3.0 mm, the ultraviolet ray permeability is poor, and the inside of the foam is not sufficiently cured.

  The winding-side upper roll 35 is provided above the supply-side lower roll 14 and is peeled off from the upper surface of the ultraviolet curable foam A by changing the direction of the upper plastic film 31 upward.

  The upper plastic film take-up roll 36 takes up the upper plastic film 31 whose direction has been changed upward by the take-up side upper roll 35.

  The lower plastic film 11 and the upper plastic film 31 can be used repeatedly after being wound up. In addition, at least one of the lower plastic film 11 and the upper plastic film 31 is UV transparent, and more preferably both are UV transparent. In the present embodiment, both the lower plastic film 11 and the upper plastic film 31 are made UV transmissive. The lower plastic film 11 and the upper plastic film 31 are preferably those that block outside air and can be peeled off from the ultraviolet curable resin.

  The ultraviolet transparent plastic film is not particularly limited as long as it can transmit ultraviolet rays. For example, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, polyurethane, ethylene vinyl acetate copolymer, ionomer, ethylene / (meth) acrylic acid copolymer A transparent plastic film made of a thermoplastic resin such as a polymer, an ethylene / (meth) acrylic acid ester copolymer, polystyrene, vinyl polyisoprene, or polycarbonate can be used. Furthermore, a plastic film made of a mixture of these resins or a laminated film of these resins may be used as long as it can transmit ultraviolet rays, that is, is transparent. The thickness of the lower plastic film 11 and the upper plastic film 31 is preferably about 25 to 100 μm.

  The ultraviolet irradiation means 41 includes an ultraviolet lamp capable of irradiating ultraviolet rays and the like, and is provided between the knife coater 34 and the winding-side upper roll 35 and is provided between the lower plastic film 11 and the upper plastic film 31. Among them, at least the ultraviolet transmissive film side is configured to be able to irradiate ultraviolet rays. In this embodiment, the upper plastic film 31 side can be irradiated with ultraviolet rays.

  The winding means of the ultraviolet curable foam is positioned in front of the winding side lower roll 15 and the winding side upper roll 35 at the front (traveling direction side) of the lower plastic film 11 in a substantially horizontal supply direction. The foam direction changing roll 42 is provided, and an ultraviolet curable foam winding roll 43 that winds the ultraviolet curable foam A whose direction is changed upward by the foam direction changing roll 42.

  The production of the ultraviolet curable foam using the production apparatus 10 will be described. First, the lower plastic film 11 is supplied from the lower plastic film supply roll 13 toward the mechanical foaming device 21, and the ultraviolet curable resin raw material P after foaming is supplied from the mechanical foaming device 21 to the lower plastic film. 11 is discharged and applied on the upper surface. In this embodiment, the lower plastic film 11 is made of a transparent material that can transmit ultraviolet rays. The ultraviolet curable resin material has the above-described configuration.

  The upper plastic film 31 is supplied from the upper plastic film supply roll 33 and laminated on the upper surface of the foamed ultraviolet curable resin material P applied to the upper surface of the lower plastic film 11. The lower end is brought into contact with the upper surface of the upper plastic film 31, and the thickness of the ultraviolet curable resin raw material P is set to a predetermined thickness between the upper plastic film 31 and the lower plastic film 11. In this embodiment, the upper plastic film 31 is made of a transparent material capable of transmitting ultraviolet rays.

  Next, the foamed ultraviolet curable resin raw material P moves to the ultraviolet irradiation means 41 in a state in which both surfaces are sandwiched between the lower plastic film 11 and the upper plastic film 31, and Is irradiated. In this embodiment, the ultraviolet curable resin material P after foaming is irradiated with ultraviolet rays from above the transparent upper plastic film 31 that can transmit ultraviolet rays. The ultraviolet curable resin raw material P after the foaming is cured by the irradiation of the ultraviolet rays, so that the ultraviolet curable foam A is obtained. At this time, since the ultraviolet curable resin raw material P after foaming is covered on both sides with the lower plastic film 11 and the upper plastic film and is prevented from coming into contact with oxygen, polymerization inhibition by oxygen (so-called oxygen inhibition) ) Can prevent the curability from becoming worse and the surface of the ultraviolet curable foam A to become sticky and sticky.

  After making into the ultraviolet curable foam A by the said ultraviolet irradiation, the said lower plastic film 11 is wound up with the said lower plastic film winding roll 16, and it peels from the lower surface of the said ultraviolet curable foam A, and also the said upper plastic film 31 is wound up by the upper plastic film winding roll 36 and peeled off from the upper surface of the ultraviolet curable foam A, and the ultraviolet curable foam A is wound up by the ultraviolet curable foam winding roll 43. Thus, the ultraviolet curable foam A is continuously produced. The ultraviolet curable foam A wound around the ultraviolet curable foam winding roll 43 is then cut into dimensions according to the application. The lower plastic film 11 wound on the lower plastic film winding roll 16 and the upper plastic film 31 wound on the upper plastic film winding roll 36 can be used repeatedly.

  Specific examples and comparative examples will be described below. Using the manufacturing apparatus 10 shown in FIG. 1, mechanically stirred with an Oaks mixer (mechanical foaming apparatus 21) while blowing nitrogen gas at a supply rate of 5 L / min into the ultraviolet curable resin material having the composition shown in Table 1. The ultraviolet curable resin raw material after foaming was applied on the lower plastic film 11, and the ultraviolet curable foams (thickness of about 1 mm) of Examples and Comparative Examples were produced as described above. The mixer rotation speed is 400 rpm, and the raw material supply rate is 240 g / min.

The oligomers in Table 1 are polyurethane methacrylate composed of polyether polyol and aliphatic isocyanate, bifunctional, molecular weight 10,000, and are manufactured in-house. Diluent 1 is morpholine acrylate (chemical structure shown in Chemical Formula 1), monofunctional, molecular weight 141, product name: ACMO, manufactured by Kojin Co., Ltd., Diluent 2 is DMAA, [CH ₂ = CHCON (CH ₃ ) ₂ ] , monofunctional molecular weight 99, Co. Kohjin Ltd., diluent 3 lauryl _{acrylate, [CH 2 = CHCOO- (CH} 2) 11 -CH 3], 1 functional, molecular weight 240, manufactured by Shin-Nakamura chemical Co., Ltd., diluent 4 polytetramethylene _{glycol, [CH 2 = COCO- (C} 4 H 8 O) 4 -COCH = CH 2, 2 -functional, molecular weight 774, product name: PTMG65, made by Shin-Nakamura chemical Co., is there. Diluent 1 and Diluent 2 are monofunctional monomers having an acrylamide group in the present invention. The ultraviolet polymerization initiator is 2-hydroxy-2-methyl-1-phenyl-propan-1-one, molecular weight 164.2, product name: Darocur 1173, manufactured by Ciba Specialty Chemicals, and the foam stabilizer is polyether-modified poly Siloxane, product name: TEGOSTAB B8110, manufactured by Goldschmidt.

Examples 1 to 3 are examples in which the amount of diluent 1 (morpholine acrylate) was changed in the range of 20 to 40 parts by weight. Example 4 was diluent 2 (DMAA, [CH ₂ = CHCON (CH ₃ ) ₂ )). Comparative Example 1 is an example in which the amount of diluent 1 (morpholine acrylate) is excessively 50 parts by weight, Comparative Example 2 is an example in which the amount of diluent 1 (morpholine acrylate) is excessively small as 10 parts by weight, Comparative Example 3 Is an example using diluent 3 (lauryl acrylate), and Comparative Example 4 is an example using diluent 4 (polytetramethylene glycol).

The lower plastic film 11 and the upper plastic film 31 are transparent polyethylene terephthalate and have a thickness of 100 μm. The ultraviolet irradiation means 41 is a mercury lamp (120 w / cm), an integrated amount of 460 mJ / cm ² (250 nm), The supply speed (movement speed) of the side plastic film 11 and the upper plastic film 31 is 7 m / min, and the distance between the knife coater 34 and the lower plastic film 11 is 1.0 mm.

About the ultraviolet curable foam of an Example and a comparative example, density (JISK7222: 1999 conformity, unit [kg / m < ³ >]), tensile strength (JISK6400 conformity, unit [MPa]), elongation (JISK6400 conformity) , [%]).

Moreover, the amount of the sticking substance causing the surface tackiness of the ultraviolet curable foams of Examples and Comparative Examples was measured by an acetone extraction method. In the acetone extraction method, 100 × 100 × 0.5 mm test pieces were cut from the UV-cured foams of the above examples and comparative examples, and the test pieces were further pulverized, and 2 g (W ₀ ) was finely pulverized. The sample was weighed, placed in a cylindrical filter paper, set in an extraction tube of a Soxhlet acetone extraction test apparatus, and extracted in 10 ml of acetone under reflux for 2 hours. After extraction, the tar content extracted in the Soxhlet flask was dried at 105 ° C. for 1 hour, and the weight after drying (W ₁ ) was precisely weighed. The acetone extraction amount R (%) is calculated by R = (W ₁ / W ₀ ) × 100. In addition, when there is much quantity of an adhesive substance (acetone extraction amount), it will come to produce surface adhesiveness (stickiness) in an ultraviolet curable foam.

  The measurement results of density, tensile strength, elongation, and acetone extraction amount are shown in the lower part of Table 1. As understood from the measurement results in Table 1, Examples 1 to 4 had high tensile strength, good elongation, and neither physical property was inferior. On the other hand, Comparative Examples 1 to 4 were inferior in tensile strength and elongation, and none of them was good. For example, the comparative example 3 using the diluent 3 made of a monomer having low reactivity has a low tensile strength, and the comparative example 4 using the diluent 4 made of a bifunctional monomer has a poor elongation. Further, Comparative Example 1 in which the amount of Diluent 1 (morpholine acrylate) is 50 parts by weight exhibits poor elongation, while Comparative Example 2 in which the amount of Diluent 1 (morpholine acrylate) is 10 parts by weight has a tensile strength. Lower. From this, the amount of the diluent composed of a monofunctional monomer having an acrylamide group is preferably 20 to 40 parts by weight in 100 parts by weight of the total of the oligomer and the diluent. In both the examples and the comparative examples, the ultraviolet curable resin material after foaming is cured by being irradiated with ultraviolet rays in a state where the upper and lower sides are covered with a plastic film and contact with oxygen is prevented. Therefore, the measurement result of the acetone extraction amount is less than 10%, and there is no surface tackiness (stickiness). Thus, the ultraviolet curable foams of Examples 1 to 4 had good flexibility, high strength, and no stickiness.

  In addition, although the said Example did not add the colorant, the colorant is suitably added according to the color calculated | required by the ultraviolet curable foam. The amount of the colorant is appropriately determined. For example, in the formulations of Examples 1 to 4 shown in Table 1, the substance name: titanium oxide, product number: UT white 4973, manufactured by Sanyo Dye Co., Ltd. is used as a white colorant in a total of 100 parts by weight of oligomer and diluent. An example in which 0.1 to 5 parts by weight is added is given.

It is a schematic front view of the manufacturing apparatus which manufactures an ultraviolet curable foam continuously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11,31 Plastic film 21 Mechanical foaming apparatus 41 Ultraviolet irradiation means A Ultraviolet curable foam P Mechanically foamed ultraviolet curable resin raw material

Claims (4)

In an ultraviolet curable foam obtained by mechanically foaming an ultraviolet curable resin raw material containing an oligomer, a diluent, an ultraviolet polymerization initiator, and a foam stabilizer, and cured with ultraviolet rays,
An ultraviolet curable foam, wherein the diluent comprises a monofunctional monomer having an acrylamide group.   The ultraviolet curable foam according to claim 1, wherein the oligomer has an acrylate group or a methacrylate group at a terminal and has a molecular weight of 8,000 to 40,000. The ultraviolet curable foam according to claim 1 or 2, having a density of 400 to 700 kg / m ³ , an elongation of 100 to 200%, and a tensile strength of 1.0 to 2.0 MPa. Ultraviolet curable resin raw material containing oligomer, monofunctional monomer with acrylamide group, UV polymerization initiator, foam stabilizer is mechanically foamed,
The foamed ultraviolet curable resin raw material is applied to one of two plastic films, at least one of which has ultraviolet transparency,
Laminating the other plastic film on the surface of the ultraviolet curable resin raw material,
The ultraviolet curable resin raw material is cured by irradiating ultraviolet rays through the ultraviolet transparent plastic film to form an ultraviolet curable foam,
Thereafter, the two plastic films are peeled off from the ultraviolet curable foam.

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