JP2014084394A - Method for producing photo-setting expanded material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a photo-setting expanded material, by which the production cost thereof can be reduced.SOLUTION: The method for producing a photo-setting expanded material includes: a mixing step in which polythiol having a plurality of thiol group, urethane prepolymer having at its terminals a plurality of functional group that activates radical addition reaction with the thiol group, and gas are mixed by mechanical foaming; a flow-casting step in which the mixed raw material is flow-casted onto a thermoplastic resin film 34; and a light irradiation step in which the flow-casted raw material is irradiated with light using a light irradiator 30, without being covered with sheet-like cover material, and is thereby set. By this method, since no acrylic raw material is contained in the photo-setting expanded material raw material, it becomes possible to employ a gas containing oxygen, i.e. air, as the gas to be mixed by mechanical foaming. Also, in the production process, it becomes possible to omit the step to cover the raw material with cover material and to simplify the production system. According to the present invention, therefore it becomes possible to achieve a reduction in production cost.

Description

  The present invention relates to a method for producing a photocured foam obtained by irradiating light to a urethane prepolymer mixed with a gas by a mechanical froth method.

  Examples of the foam made from a urethane prepolymer include a photocured foam obtained by irradiating light to a urethane prepolymer mixed with a gas by a mechanical floss method. Specifically, as described in the following patent document, raw materials containing an acrylated urethane prepolymer and a gas are mixed with a mixer or the like and mechanically foamed. And a light hardening foam is shape | molded by irradiating light to the foamed raw material.

JP 2008-101149 A Japanese Patent Laid-Open No. 62-119236

  In the photocured foam described in the above-mentioned patent document, the urethane prepolymer as the main raw material is acrylated, but the acrylic raw material has a property that it is difficult to cure due to reaction inhibition by oxygen. For this reason, a gas containing oxygen, that is, air cannot be employed as the gas mixed by the mechanical froth method, and it is necessary to employ an inert gas such as nitrogen or carbon dioxide.

  Moreover, when the raw material of a foam contains an acrylic raw material, the system for producing the foam tends to be complicated. Specifically, for example, when a sheet-like photocured foam is formed, a raw material foamed by mechanical foaming is cast on a sheet-like substrate. Then, the upper surface of the cast raw material is covered with a sheet-like covering material so that the cast raw material is not exposed to air. That is, when manufacturing a sheet-like photocured foam containing an acrylic raw material, the foamed raw material needs to be manufactured in a state of being sandwiched between a sheet-like base material and a sheet-like covering material. For this reason, the system for manufacturing a foam requires a mechanism for sending out a covering material for covering the foam raw material.

  As described above, when manufacturing a photocured foam containing an acrylic raw material, it is difficult to reduce the manufacturing cost due to the use of an inert gas and the complexity of the manufacturing system. This invention is made | formed in view of such a situation, and makes it a subject to provide the manufacturing method of the photocurable foam which can reduce manufacturing cost.

  In order to solve the above problems, the photocured foam production method of the present invention has (a) a polythiol having a plurality of thiol groups, and (b) a plurality of functional groups having radical addition reaction activity at the terminal. A casting process in which a urethane prepolymer and (c) a gas are mixed by a mechanical floss method, and the urethane prepolymer and the polythiol mixed in the mixing process are cast on a sheet-like substrate. The functional group and the thiol group are irradiated by irradiating light without covering the sheet, and the urethane prepolymer and the polythiol cast on the substrate. And a light irradiation step for carrying out a polymerization reaction, and producing a photocured foam.

  In the photocurable foam production method of the present invention, since the acrylic raw material is not included in the raw material of the photocurable foam, the light is cast without covering the raw material cast on the base material. Irradiated. And the foamed raw material hardens | cures by the photopolymerization reaction of a functional group and a thiol group, and a photocuring foam is manufactured. Therefore, according to the photocured foam manufacturing method of the present invention, the manufacturing system can be simplified. Moreover, since the acrylic raw material is not contained in the raw material of the photocured foam, a gas containing oxygen, that is, air can be employed as the gas mixed by the mechanical floss method. This makes it possible to reduce the manufacturing cost.

It is the figure which showed roughly the system for manufacturing a photocuring foam. It is the figure which showed roughly the air leak test apparatus for evaluating the airtightness of a photocuring foam. It is a figure which shows the compounding quantity (weight ratio) of the raw material for manufacturing the photocurable foam of Examples 1-4, and the physical-property evaluation of the photocurable foam of Examples 1-4. It is a figure which shows the physical-material evaluation of the compounding quantity (weight ratio) of the raw material for manufacturing the photocurable foam of Comparative Examples 1-5, and the photocurable foam of Comparative Examples 1-5. It is a figure which shows the compounding quantity (weight ratio) of the raw material for manufacturing prepolymer AF shown in FIG. 3 and FIG.

  The “photocured foam production method” of the present invention comprises (a) a polythiol having a plurality of thiol groups, (b) a urethane prepolymer having a plurality of functional groups having a thiol group and radical addition reaction activity at the terminal, c) Mixing step of mixing gas by mechanical flossing method, casting step of casting the mixed raw material on a sheet-like base material, and covering the cast raw material with a sheet-like covering material And a light irradiation step of irradiating light to produce a photocured foam. Specifically, for example, the sheet-like photocured foam 12 can be produced using the foam production apparatus 10 shown in FIG.

  The foam manufacturing apparatus 10 includes a supply roller 20, a recovery roller 22, a mixing device 24, a discharge nozzle 26, a knife coater 28, a light irradiator 30, and a gravure roller 32. A thermoplastic resin film 34 is wound around the supply roller 20, and the leading end of the thermoplastic resin film 34 is connected to the collection roller 22. Then, the supply roller 20 and the collection roller 22 rotate around their respective axes, whereby the thermoplastic resin film 34 is sent out in the direction of the arrow 36.

  The mixing device 24 has an Oaks mixer, and is a device for mixing and foaming the urethane prepolymer having the functional group at the terminal and the polythiol by a mechanical floss method. Incidentally, since the raw material of the “photocured foam” of the present invention does not contain an acrylic raw material, it is possible to employ a gas containing oxygen, that is, air, as the mixed gas.

  Then, the raw material 38 mixed and foamed by the mixing device 24 is discharged from the discharge nozzle 26 onto the thermoplastic resin film 34. The raw material 38 discharged onto the thermoplastic resin film 34 is conveyed in the direction of the arrow 36 and contacts the lower end of the knife coater 28. As a result, the raw material 38 has a predetermined thickness.

  The raw material 38 is further conveyed in the direction of the arrow 36 and reaches below the light irradiator 30. The light irradiator 30 irradiates light containing ultraviolet rays, and the raw material 38 having a predetermined thickness is irradiated with light containing ultraviolet rays. The enethiol reaction occurs by irradiation with light including ultraviolet rays, and the mixed and foamed raw material 38 is cured. Thereby, the sheet-like photocuring foam 12 is manufactured.

  Subsequently, the photocured foam 12 is conveyed in the direction of the arrow 36, and a blocking preventing release agent is applied to the surface of the photocured foam 12 by the gravure roller 32. Incidentally, examples of the antiblocking release agent include urethane acrylate resins, silicone resins, and epoxy resins. Then, the photocured foam 12 having a release agent applied to the surface is wound around the collection roller 22 together with the thermoplastic resin film 34. Thereby, the sheet-like photocured foam 12 is manufactured in a state of being wound together with the thermoplastic resin film 34.

  In addition, the process performed in the mixing apparatus 24 is a mixing process, and the process performed by the discharge nozzle 26 is a casting process. And the process performed by the light irradiation device 30 is a light irradiation process. Furthermore, the process performed by the gravure roller 32 is a coating process, and the process performed by the collection roller 22 is a winding process. By this winding process, the sheet-like photocured foam 12 is wound up in a roll shape, and the photocured foam 12 can be made compact. In addition, the wound photocured foam 12 can be easily returned to the sheet-shaped photocured foam 12 by the coating process.

  As the thermoplastic resin film 34, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polybutylene terephthalate, polyurethane, ethylene vinyl acetate copolymer, ionomer, ethylene -Resin films such as (meth) acrylic acid copolymer, ethylene / (meth) acrylic acid ester copolymer, polystyrene, vinyl polyisoprene, and polycarbonate. However, in the foam manufacturing apparatus 10, the photocuring foam 12 is manufactured by a photopolymerization reaction, and a raw material that generates high reaction heat is not used as the raw material of the photocuring foam 12, so the melting points are compared. It is possible to employ a low thermoplastic resin film. Specifically, a thermoplastic resin film 34 such as polyethylene having a melting point of 80 to 130 ° C. and biaxially stretched polypropylene can be employed. In addition, the thickness of the thermoplastic resin film 34 is preferably about 10 to 100 μm.

  Further, when the foamed raw material is cured by irradiation with ultraviolet rays and the foam is produced, the foam shrinks, but the shrinkage rate is desirably low. For this reason, the shrinkage | contraction rate of the foam at the time of foam manufacture was measured according to the thermo equipment analysis method (TMA). Specifically, the mixed and foamed raw material is applied onto a quartz plate, and an expansion / compression probe is brought into contact with the raw material. Then, after irradiating ultraviolet rays from below the quartz plate, the shrinkage rate is calculated. The shrinkage rate is the ratio of the shrinkage length in the predetermined direction of the foam before and after ultraviolet irradiation to the length in the predetermined direction of the foam before ultraviolet irradiation. The shrinkage is preferably 1.0% or less, and more preferably 0.6% or less.

  The photocured foam produced by the “photocured foam production method” of the present invention is a mixture of a urethane prepolymer having a plurality of the above functional groups, a polythiol having a plurality of thiol groups, and a gas by a mechanical floss method. And obtained by photopolymerizing the functional group and the thiol group. The urethane prepolymer having a plurality of the above functional groups at the terminal is obtained by adding the above functional group to the terminal of the urethane prepolymer obtained by the synthesis of polyisocyanate and polyol.

  The polyol that is a raw material of the urethane prepolymer is a compound having two or more hydroxyl groups in one molecule, and examples thereof include polyester polyols and polyether polyols. Some polyester polyols are obtained by a condensation reaction between a polyhydric alcohol and a polycarboxylic acid. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, butanediol, butylene glycol, glycerin, trimethylolpropane, and the like, and these can be used alone or in combination of two or more. Examples of the polyvalent carboxylic acid include glutaric acid, adipic acid, maleic acid, terephthalic acid, and isophthalic acid, and these can be used alone or in combination of two or more. Furthermore, the polyester polyol obtained by ring-opening condensation of caprolactone, methylvalerolactone, etc. is mentioned.

  Examples of polyether polyols include addition polymerization of oxides such as ethylene oxide, propylene oxide, trimethylene oxide, and butylene oxide to polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, glycerin, trimethylolpropane, and sorbitol. Can be mentioned. It is possible to use one or a combination of two or more of these various polyols as a raw material for the urethane prepolymer.

  The polyisocyanate that is a raw material of the urethane prepolymer is a compound having two or more isocyanate groups in one molecule, and examples thereof include aromatic isocyanate, aliphatic isocyanate, and alicyclic isocyanate. Examples of the aromatic isocyanate include toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), polymeric MDI (crude MDI), xylylene diisocyanate, 1,5-naphthalene diisocyanate, and the like. Examples of the aliphatic isocyanate include hexamethylene diisocyanate, isopropylene diisocyanate, and methylene diisocyanate. Examples of the alicyclic isocyanate include cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate (hydrogenated MDI), and the like. A combination of one or more of these various polyisocyanates can be used as a raw material for the urethane prepolymer.

  Moreover, it is preferable to use a catalyst in the synthesis | combination of the said urethane prepolymer. The catalyst is not particularly limited as long as it is normally employed as a raw material for the urethane prepolymer, and examples thereof include amine-based catalysts and organometallic catalysts. Examples of the amine catalyst include triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, and the like. Examples of the organometallic catalyst include star octoate, dibutyltin dilaurate, lead octenoate, potassium octylate and the like. A combination of one or more of these various catalysts can be used as a raw material for the urethane prepolymer.

  The weight average molecular weight of the urethane prepolymer obtained by the synthesis of the polyisocyanate and the polyol is preferably 1000 to 15000. Furthermore, it is preferable that it is 2500-12000, and it is especially preferable that it is 3000-5000. The number of functional groups is preferably 1.5 to 2.5, and particularly preferably 2.

  Moreover, the said functional group is added to the terminal of the urethane prepolymer obtained by the synthesis | combination of polyisocyanate and a polyol. Specifically, the functional group is added to the isocyanate group of the urethane prepolymer. The compound capable of adding the above functional group to the isocyanate group includes a compound having a vinyl group, a compound having a double bond having a cyclic strain, a compound having an unsaturated double bond, and more specifically, a vinyl ether group and an allyl ether group. And a compound having at least one of norbornene derivatives. Specific examples include allyl ether glycol, hydroxyethyl allyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, norbornene derivatives having at least one hydroxyl group in the molecule, and the like.

  The polythiol that undergoes a photopolymerization reaction with the urethane prepolymer having the functional group added to the terminal may be any one having a plurality of thiol groups that undergo an enethiol reaction with the functional group. Examples thereof include esters of mercaptocarboxylic acid and polyhydric alcohol, aliphatic polythiols, and aromatic polythiols. Examples of the aliphatic polythiol and aromatic polythiol include ethanedithiol, propanedithiol, hexamethylenedithiol, decamethylenedithiol, tolylene-2,4-dithiol, xylenedithiol and the like.

  In the ester of mercaptocarboxylic acid and polyhydric alcohol, examples of mercaptocarboxylic acid include thioglycolic acid and mercaptopropionic acid, and examples of polyhydric alcohol include ethylene glycol, propylene glycol, 1,4-butanediol, , 6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, sorbitol and the like. Among these, an ester of a mercaptocarboxylic acid and a polyhydric alcohol is preferable in terms of low odor. Specifically, for example, trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3 -Mercaptopropionate), tetraethylene glycol bis (3-mercaptopropionate), dipentaerythritol hexa (3-mercaptopropionate). In addition, it is possible to use what used together 1 type or 2 types or more of these various polythiols as a raw material of enethiol reaction with the said functional group.

  Moreover, it is preferable that the weight average molecular weight of the polythiol used as a raw material of enethiol reaction with the said functional group is 100-500. Furthermore, it is preferable that it is 200-400. Moreover, it is preferable that the number of functional groups is 2-4.

  The amount of the thiol group of the polythiol used as a raw material for the enethiol reaction with the functional group is not particularly limited, but the ratio of the number of moles of the thiol group to the number of moles of the functional group of the urethane prepolymer (ene / It is preferable that the thiol ratio is 0.8 to 1.7. Furthermore, it is preferably 1.2 to 1.4, and particularly preferably 1.3. The amount of thiol group can also be indicated by a thiol index. The thiol index is a value obtained by multiplying the ratio of the number of moles of thiol groups in the thiol compound to the number of moles of unsaturated bonding groups by 100, and is preferably 80 to 170. Furthermore, it is preferable that it is 120-140, and it is especially preferable that it is 130.

  In addition, in order to effectively perform the photopolymerization reaction between the functional group added to the urethane prepolymer and the thiol group, the raw material of the “photocured foam” of the present invention may contain a photopolymerization initiator. preferable. Examples of the photopolymerization initiator include acetophenone-based, benzophenone-based, and thioxanthone-based compounds. As the acetophenone series, for example, 2,2-dimethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 4- (1-t-butyldioxy-1-methylethyl) acetophenone, 2-methyl-1- [4- (Methylthio) phenyl] -2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, diethoxyacetophenone, 2-hydroxy-2-methyl- 1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1 -[4- (1-Methylvinyl) phenyl] propanone oligomer And the like.

  Examples of the benzophenone series include 4- (1-t-butyldioxy-1-methylethyl) benzophenone, 3,3 ′, 4,4′-tetrakis (t-butyldioxycarbonyl) benzophenone, and methyl o-benzoylbenzoate. 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3 ', 4,4'-tetra (t-butylperoxylcarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4- Examples include benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethananium bromide, (4-benzoylbenzyl) trimethylammonium chloride, and the like. Examples of the thioxanthone series include 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichloro. Examples include thioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride.

  In addition, it is preferable that content of a photoinitiator is 0.01-5 mass parts per 100 mass parts in total of the said urethane prepolymer and thiol, and if it says further, it will be 0.1-3 mass parts Is preferred. If the content of the photopolymerization initiator is too small, the photopolymerization initiation ability is insufficient, and the raw material is not rapidly polymerized, which is not preferable. On the other hand, if the content of the photopolymerization initiator is too large, polymerization is excessively promoted, the crosslinking density becomes too high, or the crosslinked structure is formed unevenly, which is not preferable.

  In the “photocured foam production method” of the present invention, as described above, the photocured foam is produced with almost no heat. For this reason, the air bubbles formed at the time of foaming are cured without being crushed, and many air bubbles remain independently. From this, the photocured foam produced by the “photocured foam production method” of the present invention can be used for various applications, but it can be used as a sealing material, a buffer material, a heat insulating material, and the like. preferable.

  When the photocured foam is used as a sealing material, a cushioning material or the like, it is desirable that the foam is flexible to some extent and easily returns to its original shape. The softness of the foam is evaluated by the compression hardness (at 25% compression) (MPa) obtained by a measurement method based on the JIS K 6254: 2010 B method. The compression hardness (at 25% compression) (MPa) indicates that the smaller the value, the more flexible, and in the photocured foam produced by the “photocured foam production method” of the present invention, 0.05 MPa or less, more preferably 0.03 MPa or less. The ease of restoring the foam to the original shape is evaluated by the compressive residual strain (%) obtained by the measurement method based on the JIS K 6400-4: 2004 A method. The compressive residual strain (%) indicates that the smaller the numerical value, the easier it is to restore. In the photocured foam produced by the “photocured foam production method” of the present invention, it is 20% or less. It is preferable that it is 10% or less.

  Moreover, when using a photocuring foam as a sealing material, it is desirable that the airtightness by a photocuring foam is high. The airtightness evaluation test is performed using an air leak test apparatus 50 shown in FIG. The air leak test apparatus 50 includes a housing 52, a generally cylindrical air leak member 54, a generally disc-shaped compression plate 56, a coupling mechanism 58 that couples the air leak member 54 and the compression plate 56, and air into the housing 52. The pump 60 for feeding in and the barometer 62 which measures the air pressure in the housing 52 are comprised. The air leak member 54 is attached in the housing 52 so as to open at the top of the housing 52. The compression plate 56 is coupled to the lower end of the air leak member 54 by a coupling mechanism 58 and is movable upward. In addition, the pump 60 sends air into the housing 52 and raises the air pressure in the housing 52 to a predetermined height.

  In the air leak test apparatus 50 having such a structure, a test piece (thickness 500 μm, outer diameter 25 mm, inner diameter 11 mm) 64 obtained by cutting a photocured foam into a donut shape is placed on the compression plate 56, 56 is moved upward. Then, the test piece 64 is compressed by the upper surface of the compression plate 56 and the lower end of the air leak member 54 to a thickness of 400 μm. Subsequently, the pump 60 is operated to increase the air pressure in the housing 52 to 20 kPa. And it is left in that state, and the time until the air pressure in the housing 52 drops to 18 kPa or less is measured. Incidentally, the air in the housing 52 leaks out of the housing 52 from between the air leak member 54 and the test piece 64 and between the compression plate 56 and the test piece 64 through the inside of the air leak member 54. The longer the measured time, the higher the airtightness. In the “photocured foam” of the present invention, it is preferably 120 seconds or longer.

  Moreover, when using a photocuring foam as a sealing material, it is desirable that the water-stopping property by a photocuring foam is also high. The water stopping property is evaluated according to the method shown below. A test piece (thickness 500 μm, outer diameter 25 mm, inner diameter 11 mm) obtained by cutting a photocured foam into a donut shape is sandwiched between two acrylic plates (thickness 3 mm, 50 mm × 50 mm), and the thickness of the test piece is 400 μm. Close the two acrylic plates until Then, the test piece sandwiched between the two acrylic plates is immersed in a water tank having a depth of 1 m for 30 minutes, and the degree of penetration of water into the inner diameter portion of the donut-shaped test piece is visually evaluated. In the “photocured foam” of the present invention, it is preferable that no water permeates into the inner diameter of the test piece.

  Moreover, when using a photocuring foam as a sealing material, it is desirable that the water absorption of a foam is low. The water absorption is evaluated by the water absorption rate (%) obtained by the measurement method based on JIS K 7209. Specifically, the photocured foam (thickness: 500 μm, 50 mm × 50 mm) is immersed in a water bath with a water depth of 100 mm and filled with water having a water temperature of 23 ± 2 ° C. for 24 hours, and the rate of change in weight is measured. The measurement rate, that is, the water absorption rate (%) indicates that the smaller the value, the lower the water absorption. In the “photocured foam” of the present invention, it is preferably 30% or less, In other words, it is preferably 25% or less.

  The following examples illustrate the present invention more specifically. However, the present invention is not limited to this embodiment, and can be implemented in various modes with various modifications and improvements based on the knowledge of those skilled in the art.

<Raw material and production of photocured foam>
Photocured foams of Examples 1 to 4 and Comparative Examples 1 to 5 were produced from the raw materials having the formulations shown in FIGS. 3 and 4. Below, the detail of each raw material is shown.

  Each “prepolymer” shown in FIG. 3 and FIG. 4 can be obtained by reacting the raw materials having the composition (weight ratio) shown in FIG. 5 according to the following method.

  First, the amount of polyol shown in the figure is put into a 1-liter separable flask, and the amount shown in the figure is added while stirring the polyisocyanate while flowing nitrogen. After confirming that the contents are uniform, a catalyst (0.3 g) is added. And it heats up slowly so that it may become 80-90 degreeC over 1 hour. Two hours after raising the temperature to the target temperature, the isocyanate group content is measured according to a method (polyurethane raw material aromatic isocyanate test method) based on JIS Z1603-1: 2007. The measured value confirms that a predetermined amount of isocyanate is consumed. When the isocyanate consumption is less than the predetermined amount, the reaction time is extended.

  After confirming that a predetermined amount of isocyanate is consumed, vinyl ether or methacrylate is slowly added dropwise in the amount shown in the figure, and the reaction is carried out for 2 hours. After the elapse of 2 hours, the isocyanate group content is measured again according to the above method, and it is confirmed whether or not the isocyanate is completely consumed. Each “prepolymer” shown in the figure is obtained on the condition that consumption of isocyanate is confirmed.

Polyol; polyoxypropylene glycol, trade name: Sannix PP-3000, manufactured by Sanyo Chemical Co., Ltd., weight average molecular weight: 3000, number of hydroxyl groups: 2
Polyisocyanate; TDI (2,4-TDI: 2,6-TDI = 80: 20), trade name: T-80, manufactured by Mitsui Chemicals, Inc. Vinyl ether; 4-hydroxybutyl vinyl ether, trade name: HBVE, BASF Japan-made methacrylate; 2-hydroxyethyl methacrylate, trade name: HEMA, manufactured by Nippon Shokubai Co., Ltd.

Each prepolymer obtained as described above and polythiol, monofunctional acrylate monomer, photopolymerization initiator, and foam stabilizer described later are weighed so as to have a blending ratio (weight ratio) shown in FIG. And according to the manufacturing method substantially the same as the manufacturing method mentioned above, a photocurable foam is manufactured. Briefly, first, the weighed raw material and air are mixed and stirred using an Oaks mixer and mechanically foamed. Then, the foamed raw material is cast on the thermoplastic resin film, and the thickness of the raw material is set to 500 μm using a knife coater. Then, UV irradiation is performed with a UV lamp (high pressure mercury lamp) at 1200 mJ / cm ² (365 nm integrated light amount). Thereby, a photocuring foam is obtained.

  However, regarding the photocured foams of Comparative Examples 1 to 5, when the thermoplastic resin film was produced in a state where only one side of the foam was covered, an uncured material layer was formed on the foam surface, and the hard coat was peeled off. End up. For this reason, at the time of manufacturing the photocured foams of Comparative Examples 1 to 5, the foamed raw material was cast on the thermoplastic resin film, and the foamed raw material was cast after the thickness of the raw material was 500 μm using a knife coater. A thermoplastic resin film is placed on the substrate. And a UV irradiation is performed to a foaming raw material through a thermoplastic resin film. That is, UV irradiation is performed in a state where thermoplastic resin films are laminated on the upper and lower surfaces of the foaming raw material.

  In addition, as a thermoplastic resin film used at the time of photocuring foam manufacture, a polyethylene terephthalate resin film (t25 μm), a polyethylene resin film (t25 μm), and a biaxially stretched polypropylene resin film (t25 μm) Each is adopted.

Polythiol A: Number of functional groups 2, weight molecular weight 238.6, butanediol bisthioglycolate, 1,4-BDTG, manufactured by Sakai Chemical Co., Ltd. Polythiol B: number of functional groups 3, weight molecular weight 398.5, trimethylolpropane Tris (3-mercaptopropionate), TMMP, manufactured by SC Organic Chemical Co., Ltd., monofunctional acrylate monomer; acryloylmorpholine, manufactured by Kojin Co., Ltd., photopolymerization initiator; 2-hydroxy-2-methyl-1- Phenyl-propan-1-one, DAROCUR1173, manufactured by BASF, foam stabilizer; block copolymer of dimethylsiloxane and polyoxyalkylene glycol, SH-190, manufactured by Toray Dow Corning

  Incidentally, the ratio of the number of moles of thiol groups to the number of moles of vinyl ether groups of the urethane prepolymer is shown in the column of “ene / thiol ratio” in FIGS.

<Evaluation of physical properties of photocured foam>
For the urethane foam produced by the mechanical floss method of Examples 1 to 4, the photocured foam of Comparative Examples 1 to 5 and the mechanical floss method of Comparative Example 6 produced as described above, The physical properties were evaluated by the method.

In order to evaluate the foamability of the foam material, the foamability during mechanical foaming was visually evaluated. The evaluation results are shown in the “foaming” column of FIGS. Moreover, in order to evaluate the foamability of a foam raw material by a numerical value, the apparent density (kg / m ³ ) was measured according to a method based on JIS K 7222: 2005. The apparent density (kg / m ³ ) indicates that the smaller the value, the better the foamability. The apparent density (kg / m ³ ) was measured on a photocured foam produced by manually foaming. The measurement results are shown in the column of “apparent density (hand experiment)” in FIGS.

  Moreover, the wrinkles etc. of the film after foam production were evaluated visually for every film employ | adopted as a thermoplastic resin film. Specifically, as a thermoplastic resin film, when a polyethylene terephthalate resin film is employed, when a polyethylene resin film is employed, and when a biaxially stretched polypropylene resin film is employed, respectively. In FIG. 5, it is determined whether or not wrinkles or the like are generated in each film after manufacturing the foam. When no wrinkles or the like occurred, it was evaluated as “good”, and when wrinkles or the like occurred, it was evaluated as “bad”. This evaluation is shown in the columns of “film raw material: polyethylene terephthalate”, “film raw material: polyethylene”, and “film raw material: biaxially oriented polypropylene” in FIGS.

  Furthermore, the exothermic temperature (° C.) of the raw material during the reaction was measured in order to give reasons for the occurrence of wrinkles on the film. Specifically, a thermocouple thermometer was inserted into a raw material having a thickness of 500 μm using a knife coater on a thermoplastic resin film, and the maximum temperature during UV irradiation was measured. The measurement results are shown in the column of “Exothermic temperature during reaction” in FIGS.

  In order to evaluate the airtightness of the foam, the above-described air leak test was performed using the air leak test apparatus 50 shown in FIG. The measurement result of the test is shown in the column of “Air Leakage” in FIGS. 3 and 4.

  Moreover, the water-stopping property of the foam was evaluated according to the following method. A test piece (thickness 500 μm, outer diameter 25 mm, inner diameter 11 mm) obtained by cutting a photocured foam into a donut shape is sandwiched between two acrylic plates (thickness 3 mm, 50 mm × 50 mm), and the thickness of the test piece is 400 μm. Close the two acrylic plates until Then, the test piece sandwiched between the two acrylic plates is immersed in a water tank having a depth of 1 m for 30 minutes, and the degree of penetration of water into the inner diameter portion of the donut-shaped test piece is visually evaluated. When water did not enter the inner diameter portion, it was evaluated as “◯”, and when water entered the foam itself, it was evaluated as “Δ”. This evaluation is shown in the “water-stop” column of FIGS. 3 and 4.

  In order to evaluate the water absorption of the foam, the water absorption (%) was measured in accordance with a method based on JIS K 7209. Specifically, the photocured foam (thickness: 500 μm, 50 mm × 50 mm) was immersed in a water bath with a water depth of 100 mm and filled with water having a water temperature of 23 ± 2 ° C. for 24 hours, and the rate of change in weight was measured. The measurement results are shown in the column of “Water absorption” in FIGS.

  In order to evaluate the restoring force of the foam during compression, compression residual strain (%) was measured according to a method based on JIS K 6400-4: 2004 A method. The measurement results are shown in the “compressed residual strain” column of FIGS.

  In order to evaluate the flexibility of the foam, the compression hardness (at 25% compression) (MPa) was measured according to a method based on JIS K 6254: 2010 B method. The measurement result is shown in the column of “25% compressive load” in FIGS. 3 and 4.

  Further, in order to evaluate the moldability of the photocured foam, the shrinkage rate (%) was measured. Specifically, a foam material mixed and foamed is applied on a quartz plate of a thermal instrument analyzer, and an expansion / compression probe is brought into contact with the raw material. Then, after irradiating ultraviolet rays from below the quartz plate, the shrinkage rate is calculated. The shrinkage rate is the ratio of the shrinkage length in the predetermined direction of the foam before and after ultraviolet irradiation to the length in the predetermined direction of the foam before ultraviolet irradiation. The calculation result is shown in the column of “shrinkage rate” in FIGS. 3 and 4.

  Furthermore, in order to evaluate the moldability of the photocured foam, the surface of the foam after ultraviolet irradiation was visually evaluated. The evaluation results are shown in the “foam surface state” column of FIGS. 3 and 4.

  From the above evaluation results, it can be seen that by using a monofunctional acrylate monomer as a raw material of the foam, the exothermic temperature at the time of the reaction increases, and the foam cannot be produced appropriately. Specifically, the foams of Comparative Example 4 and Comparative Example 5 have a higher exothermic temperature during the reaction than the foams of Examples 1 to 4. Therefore, as a thermoplastic resin film on which the foaming raw material is cast, a polyethylene terephthalate resin film, a polyethylene resin film, or a biaxially stretched polypropylene resin film may be used. Due to the high heat of reaction, the film shrinks and wrinkles occur on the surface of the foam.

  Moreover, by adopting a monofunctional acrylate monomer as a raw material of the foam, not only the shrinkage of the film but also the photocured foam is shrunk. Specifically, as can be seen from FIGS. 3 and 4, the foams of Comparative Example 4 and Comparative Example 5 have a higher shrinkage (%) than the foams of Examples 1 to 4. . For this reason, it is difficult to appropriately mold the photocured foam.

Furthermore, it is understood that the foamability is lowered by adopting a monofunctional acrylate monomer as a raw material of the foam. Specifically, in the foams of Comparative Examples 4 and 5, the visual foamability is good, but compared with the foams of Examples 1 to 4, the apparent density (kg / m ³ ). Is expensive. That is, in the foams of Comparative Example 4 and Comparative Example 5, the foamability is low.

  On the other hand, in the foams of Examples 1 to 4, since no monofunctional acrylate monomer is used as a raw material, the exothermic temperature during the reaction is relatively low. As a result, a foam is appropriately produced even when any of a resin film made of polyethylene terephthalate, a resin film made of polyethylene, or a resin film made of biaxially stretched polypropylene is adopted as the thermoplastic resin film. It is possible to do. Incidentally, the melting point of polyethylene terephthalate is 260 degrees, the melting point of polyethylene is approximately 80 to 90 degrees, and the melting point of biaxially stretched polypropylene is approximately 100 ° C. That is, it is possible to employ a thermoplastic resin film having a relatively low melting point such as polyethylene and biaxially stretched polypropylene when the foams of Examples 1 to 4 are manufactured.

Moreover, in the foams of Examples 1 to 4, as can be seen from FIGS. 3 and 4, the shrinkage rate (%) is low compared to the foams of Comparative Examples 4 and 5. It is possible to appropriately mold a photocured foam. Furthermore, in the foams of Examples 1 to 4, the apparent density (kg / m ³ ) is lower and the foamability is better than the foams of Comparative Example 4 and Comparative Example 5.

  Moreover, in the foam of Comparative Examples 1-5, since prepolymer D-F is employ | adopted as a raw material, the foam is manufactured in the state which laminated | stacked the thermoplastic resin film on the upper and lower surfaces of a foam raw material. This is because the acrylic material has a property that it is difficult to cure due to reaction inhibition by oxygen, and the prepolymers D to F are provided with an acrylic group at the end of the prepolymers D to F by containing methacrylate. It is to be done. Thus, even if the foam is molded in a state where the upper and lower surfaces of the foam material are covered with the film, in the foam of Comparative Example 3, a foam having a sticky surface is formed. This is considered that air, that is, a gas containing oxygen and a prepolymer are mixed and stirred at the time of mechanical foaming of the foam material, so that a foam having a sticky surface is formed.

  For this reason, when an acrylic raw material is included as a raw material of the foam, it is necessary to employ an inert gas such as nitrogen or carbon dioxide as a gas to be stirred during mechanical foaming. Furthermore, it is necessary to cover the upper surface of a raw material with a film etc. at the time of foam manufacture. However, the use of an inert gas, the construction of a production line for covering the upper surface of the raw material, and the like increase the production cost, which is not desirable.

  On the other hand, in the foams of Examples 1 to 4, Prepolymer A to Prepolymer C are employed as the raw material of the foam. The raw materials of the prepolymer A to the prepolymer C include vinyl ether instead of methacrylate, and the end of the prepolymer A to the prepolymer C is provided with a vinyl group instead of the acrylic group. And the photocuring foam is manufactured because the vinyl group and the thiol group of polythiol carry out photopolymerization reaction, and a foaming raw material hardens | cures. That is, the foams of Examples 1 to 4 do not include an acrylic raw material as the foam raw material. As a result, air can be employed as the gas to be stirred during mechanical foaming without employing an inert gas such as nitrogen or carbon dioxide. Furthermore, it is not necessary to cover the upper surface of the raw material with a film or the like when manufacturing the foam. Therefore, according to the foams of Examples 1 to 4, it is possible to manufacture a suitable photocured foam while reducing the manufacturing cost.

  Moreover, in the foams of Examples 1 to 4, as can be seen from FIGS. 3 and 4, the 25% compression load (MPa) is lower than the foams of Comparative Examples 1 to 5. Yes. That is, the foams of Examples 1 to 4 are superior in flexibility as compared with the foams of Comparative Examples 1 to 5. Furthermore, the foams of Examples 1 to 4 are excellent in airtightness and waterstop, as can be seen from the evaluation of air leakage and waterstop. Furthermore, the foams of Examples 1 to 4 are excellent in restoration properties as can be seen from the evaluation of compression residual strain (%). As described above, the foams of Examples 1 to 4 have all excellent properties as a sealing material such as flexibility, airtightness, water-stopping property, and restorability. From this, it is preferable to use the foams of Examples 1 to 4 as the sealing material.

  Moreover, in the foams of Examples 1 to 4, the water absorption (%) is low as compared with the foams of Comparative Examples 4 and 5, as can be seen from FIGS. 3 and 4. That is, the foams of Examples 1 to 4 have low absorbency and further have excellent characteristics as a sealing material.

  In addition, in the urethane foam of the comparative example 6, as understood from the evaluation of the air leak property, the water-stopping property, and the water absorption rate in FIG. This is because the closed cell ratio of the urethane foam of Comparative Example 6 is low. On the other hand, since the foams of Examples 1 to 4 are manufactured by UV irradiation as described above, they are manufactured with almost no heat. For this reason, the air bubbles formed at the time of foaming are cured without being crushed, and many air bubbles remain independently. This also shows that the foams of Examples 1 to 4 are excellent as sealing materials.

  Furthermore, in the foams of Examples 1 to 3, the compression residual strain (%) is lower than that of the foam of Example 4. That is, by setting the ene / thiol ratio to about 1.3, it is possible to produce a foam that can be easily restored. In addition, since it is thought that the ease of decompression | restoration is the outstanding characteristic as a sealing material, it is especially preferable to use the foam of Example 1- Example 3 as a sealing material.

  Hereinafter, various aspects of the present invention will be listed.

(1) (a) a polythiol having a plurality of thiol groups, (b) a urethane prepolymer having a plurality of functional groups having radical addition reaction activity with the thiol group, and (c) a gas by a mechanical floss method. A mixing step of mixing;
A casting step of casting the urethane prepolymer and the polythiol mixed in the mixing step on a sheet-like substrate;
The functional group and the thiol group are allowed to undergo a photopolymerization reaction by irradiating light without covering the urethane prepolymer and the polythiol cast on the base material with a sheet-like covering material. A light curable foam production method comprising producing a photocured foam comprising a light irradiation step.

(2) The substrate is
The method for producing a photocurable foam according to item (1), wherein the thermoplastic resin film has a melting point of 80 to 130 ° C.

  (3) The photocured foam according to (1) or (2), wherein the urethane prepolymer has an average functional group number of 1.5 to 2.5.

  (4) The photocured foam production method according to any one of (1) to (3), wherein the urethane prepolymer has a weight average molecular weight of 1000 to 15000.

  (5) The method for producing a photocurable foam according to any one of (1) to (4), wherein the polythiol has an average number of functional groups of 2 to 4.

  (6) The method for producing a photocurable foam according to any one of (1) to (5), wherein the polythiol has a weight average molecular weight of 100 to 500.

  (7) The ratio of the number of moles of the thiol group to the number of moles of the functional group is 0.8 to 1.7, according to any one of (1) to (6), Photocured foam production method.

  (8) Light according to any one of items (1) to (7), wherein the compression hardness at 25% compression (JIS K6254: 2010 B method) is 0.05 MPa or less Cured foam manufacturing method.

  (9) The photocured foam production according to any one of items (1) to (8), wherein the compression residual strain (JIS K6400-4: 2004 A method) is 20% or less Method.

  (10) The method for producing a photocurable foam according to any one of (1) to (9), wherein the gas contains at least oxygen.

(11) The photocured foam production method comprises:
The method for producing a photocurable foam according to any one of (1) to (10), further comprising a winding step of winding the base material after the light irradiation step is performed.

(12) The photocured foam production method comprises:
A coating treatment step of performing a coating treatment on the urethane prepolymer and the polythiol irradiated with light in the light irradiation step;
The winding step
The method for producing a photocurable foam according to item (11), wherein the substrate is wound after the coating treatment step.

  (13) The method for producing a photocurable foam according to any one of (1) to (12), wherein the photocured foam functions as a sealing material.

  (14) The method for producing a photocurable foam according to any one of (1) to (13), wherein the functional group is a vinyl ether group.

Claims (9)

(A) A polythiol having a plurality of thiol groups, (b) a urethane prepolymer having a plurality of functional groups having radical addition reaction activity with the thiol group, and (c) a gas mixed with a mechanical floss method. Process,
A casting step of casting the urethane prepolymer and the polythiol mixed in the mixing step on a sheet-like substrate;
The functional group and the thiol group are allowed to undergo a photopolymerization reaction by irradiating light without covering the urethane prepolymer and the polythiol cast on the base material with a sheet-like covering material. A light curable foam production method comprising producing a photocured foam comprising a light irradiation step.   The method for producing a photocurable foam according to claim 1, wherein the functional group is a vinyl ether group. The substrate is
The method for producing a photocurable foam according to claim 1 or 2, wherein the thermoplastic resin film has a melting point of 80 to 130 ° C. The average number of functional groups of the urethane prepolymer is 1.5 to 2.5, and the weight average molecular weight of the urethane prepolymer is 1000 to 15000,
The average functional group number of the polythiol is 2 to 4, and the weight average molecular weight of the polythiol is 100 to 500.
4. The photocured foam according to claim 1, wherein a ratio of the number of moles of the thiol group to the number of moles of the functional group is 0.8 to 1.7. Production method. The compression hardness at the time of 25% compression (JIS K6254: 2010 B method) is 0.05 MPa or less,
The method for producing a photocurable foam according to any one of claims 1 to 4, wherein the compression residual strain (JIS K6400-4: 2004 A method) is 20% or less.   The method for producing a photocurable foam according to claim 1, wherein the gas contains at least oxygen. The photocured foam production method is
The method for producing a photocurable foam according to any one of claims 1 to 6, further comprising a winding step of winding the base material after the light irradiation step is performed. The photocured foam production method is
A coating treatment step of performing a coating treatment on the urethane prepolymer and the polythiol irradiated with light in the light irradiation step;
The winding step
The method for producing a photo-curing foam according to claim 7, wherein the substrate is wound up after the coating process is performed.   The photocured foam production method according to any one of claims 1 to 8, wherein the photocured foam functions as a sealing material.

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