JP2013256558A - Method for producing foam urethane sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing a foam urethane sheet, even if a highly reactive urethane stock solution using a highly viscous prepolymer having terminal NCO groups is used.SOLUTION: A method for producing a foam urethane sheet includes: an application step of continuously applying a reaction stock solution prepared by mixing a prepolymer derived from diphenylmethane diisocyanate and having terminal NCO groups, a foaming agent, a low-molecular polyol having a molecular weight of ≤500, an organic acid having a pKa of 3.46 to 1.00, and a heterocyclic tertiary amine, on a first continuous web 14A, to thereby form an applied film 10; and a heating step of heating the applied film on the first continuous web to cure the applied film.

Description

  The present invention relates to a method for producing a urethane foam sheet.

  Durable, such as polishing pads that precisely polish semiconductor wafers and glass substrates for displays, anti-vibration pads that prevent noise and vibration generated from railway tracks, and anti-vibration pads that are used in the fields of automobiles, construction, civil engineering, etc. A foamed urethane sheet is used as a pad that requires good properties.

  In order to produce such a foamed urethane sheet that requires durability, a prepolymer having an NCO terminal whose molecular weight is increased by reacting a polyol with an isocyanate in advance in order to improve the strength is usually used. Since the prepolymer having an NCO terminal has a high viscosity, generally a reaction stock solution obtained by mixing and stirring with a urethane raw material such as a foaming agent and a crosslinking agent at a high temperature of 50 ° C. or higher, for example, 70 ° C. is used as a mold. Then, it is heated and cured (see, for example, Patent Documents 1 to 3).

  Even when making thin products such as polishing pads and anti-vibration pads for railroads, make a product that is somewhat large and then make a thin product by slicing, etc., or use a reaction stock solution in a thin mold Currently, batch production is carried out (see, for example, Patent Documents 4 to 6). However, the method of slicing a foamed urethane elastomer by slicing from a batch product has many unnecessary waste parts, the productivity is poor, and the quality variation tends to increase.

  On the other hand, an apparatus and a method for producing a polyurethane foam by continuously applying a highly reactive polyurethane stock solution on a releasable film with a coat hanger die are disclosed (see, for example, Patent Documents 7 and 8). However, this method requires the reaction stock solution to flow through a thin coat hanger die, and the liquid viscosity must be low, and a reaction stock solution using a high viscosity prepolymer cannot be applied.

  In addition, as an improvement of the production method using a mold, Patent Document 9 discloses that a reaction stock solution is discharged between two endless track stainless steel belts, heat-cured, and the resulting foam is divided into upper and lower parts. A method for producing a polishing pad is disclosed. However, when trying to carry out such a method, the urethane reaction stock solution is highly reactive, so that the thickening proceeds in a short time. Even if it is continuously discharged between stainless steel belts, if it is applied for about 20 seconds to 2 minutes with a coating apparatus, it will gel, and long-term continuous discharge of 1 hour or more is impossible.

JP 10-17639 A JP 2008-56730 A JP 2011-38005 A JP 2002-192454 A JP 2000-343412 A JP-A-2005-068168 JP 54-81366 A JP 54-81367 A JP 2004-169038 A

  An object of the present invention is to provide a method capable of continuously producing a foamed urethane sheet even by using a highly reactive urethane stock solution using a prepolymer having a terminal NCO group having a high viscosity.

  In order to achieve the above object, the following invention is provided.

The invention of claim 1 includes a prepolymer having a terminal NCO group derived from diphenylmethane diisocyanate, a blowing agent, a low molecular polyol having a molecular weight of 500 or less, an organic acid having a pKa of 3.46 to 1.00, and a heterocyclic tertiary amine. Or a prepolymer having a terminal NCO group derived from diphenylmethane diisocyanate, a blowing agent, a low molecular polyol having a molecular weight of 500 or less, and an organic acid and a heterocyclic tertiary with a pKa of 3.46 to 1.00 A coating step of continuously coating a reaction stock solution mixed with a salt with amine on the first continuous web to form a coating film;
A heating step of heating and curing the coating film on the first continuous web;
It is a manufacturing method of the foaming urethane sheet containing this.

According to a second aspect of the present invention, a second continuous web is supplied to the coating film on the first continuous web after the coating step and before the heating step, and the coating is performed by the two continuous webs. Including a second continuous web supply step sandwiching the membrane,
The said heating process is a manufacturing method of the urethane foam sheet of Claim 1 which is a process of heating and hardening the said coating film in the state pinched | interposed by the said 2 continuous webs.

  The invention according to claim 3 is the urethane foam sheet according to claim 2, wherein at least one of the first continuous web and the second continuous web is a continuous web in which a surface in contact with the coating film has releasability. It is a manufacturing method.

  In the invention of claim 4, the organic acid having a pKa of 3.46 to 1.00 is orthophthalic acid, maleic acid or malonic acid, and the heterocyclic tertiary amine is cycloamidine or dicyclooctane. It is a manufacturing method of the foaming urethane sheet of any one of Claims 1-3.

  ADVANTAGE OF THE INVENTION According to this invention, even if it uses the highly reactive urethane stock solution using the prepolymer which has a terminal NCO group with a high viscosity, the method which can manufacture a foaming urethane sheet continuously is provided.

It is the schematic which shows an example of the apparatus structure used for the manufacturing method of the foaming polyurethane sheet of this invention.

Hereinafter, the manufacturing method of a urethane foam sheet is demonstrated concretely.
The present inventors have prepared a prepolymer having a terminal NCO group using diphenylmethane diisocyanate (MDI), a low molecular polyol having a molecular weight of 500 or less as a chain extender, a blowing agent, and an organic acid having a pKa of 3.46 to 1.00. And a heterocyclic tertiary amine or a salt thereof as a catalyst, a thin sheet-like foamed urethane elastomer is continuously used even in a urethane-reactive stock solution using a prepolymer having a high viscosity terminal NCO group. Found that can be produced.

  That is, the method for producing a foamed urethane sheet of the present invention comprises a prepolymer having a terminal NCO group derived from diphenylmethane diisocyanate (MDI), a foaming agent, a low molecular polyol, an organic acid having a pKa of 3.46 to 1.00, and a complex. A reaction stock solution mixed with a ring tertiary amine, or a prepolymer having a terminal NCO group derived from diphenylmethane diisocyanate, a blowing agent, a low molecular polyol having a molecular weight of 500 or less, and an organic acid having a pKa of 3.46 to 1.00 A step of continuously applying a reaction stock solution mixed with a salt with a heterocyclic tertiary amine on the first continuous web to form a coating film, and heating the coating film on the first continuous web. And a step of curing.

In the method for producing a foamed urethane sheet of the present invention, preferably, after the coating step and before the heating step, the second continuous web is supplied to the coating film on the first continuous web by two continuous webs. Including a second continuous web supply step for sandwiching the coating film, the heating step is a step of heating and curing the coating film in a state of being sandwiched between two continuous webs.
First, the reaction stock solution will be described.

(Prepolymer having terminal NCO group derived from MDI)
As a raw material for the urethane foam sheet, a prepolymer having a terminal NCO group derived from MDI synthesized using polyol and diphenylmethane diisocyanate (MDI) as an isocyanate (hereinafter referred to as “prepolymer having a terminal NCO group” or “ May be abbreviated as “terminal NCO group prepolymer”).
As a prepolymer having terminal NCO groups derived from MDI used in the present invention, NCO% is obtained by reacting polyol and MDI with an NCO group excess of NCO group / OH group equivalent ratio of about 1.5 to 6.0. What was made into 3 to 15% can be used conveniently.
Further, when a high hardness product is required, the concentration of polar groups can be increased by adding carbodiimide-modified liquid MDI or the like.

  Examples of the polyol used for the synthesis of the prepolymer having a terminal NCO group include polyoxyalkylene-based polyoxypropylene polyol (PPG), polyoxyethylene polyol (PEG), a copolymer of PPG and PEG, polyoxyalkylene Examples include tetramethylene polyol (PTMG). Other polyols include dicarboxylic acids such as adipic acid, sebacic acid, phthalic acid, and dimer acid, and glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and 2-methyl. Examples thereof include polyester polyols (PES) such as adipic acid ester polyol (PA) condensed with propanediol, 3-methylpentanediol and the like, polycaprolactone polyol (PCL), polycarbonate polyol (PCA) and the like.

The polyol used for the synthesis of the prepolymer having a terminal NCO group preferably has 2 to 3 functional groups and a molecular weight of 500 to 6000, and is functional from the viewpoint of ease of prepolymer synthesis, viscosity, and toughness. Particularly preferred are those having a base number of 2 to 2.5 and a molecular weight of 500 to 2500.
The polyol component has a low viscosity, and PPG, PTMG, PA, and PCL are preferable in order to increase the strength and elongation of the resulting product.

  In the present invention, the MDI used for the synthesis of the prepolymer having a terminal NCO group can preferably have a functional group number of 2 to 2.3. However, the number of functional groups is from the ease of prepolymer synthesis and the physical properties of the foam. Two are particularly preferred.

When MDI is used as an isocyanate, thickening at the beginning of mixing is slow (initial reaction rate is low). However, when heat-cured, solidification time is fast and high-speed production is possible. The fact that high-speed production is possible means that coating can be performed at a high speed, and the old reaction stock solution is washed away with a fresh reaction stock solution in the coating apparatus, so that there is an advantage that continuous coating can be performed for a long time. That is, the longer the gelation time (seconds) / solidification time (minutes) = gelation / solidification ratio, the easier it is to apply the reaction stock solution continuously.
According to experiments by the present inventors, it was found that continuous coating is possible when the gelation / solidification ratio is preferably 15 to 80. A more preferred gelation / solidification ratio is 30 to 80, and most preferred is 60 to 80. Within this range, production can be performed at a particularly high speed.

Here, the gelation time is a time required for the viscosity to reach 40,000 Pa · s at 70 ° C. by mixing a prepolymer having terminal NCO groups derived from MDI, a predetermined amount of chain extender, and a catalyst. Second to 300 seconds) is preferable.
The solidification time is that after a predetermined reaction stock solution is applied onto a resin film having releasability, the same releasable resin film is placed on the upper surface of the coating film, and heated at 100 ° C. to solidify. The time when the resin film can be peeled off.
In general, the shorter the gelation time, the thicker the raw material becomes during coating, and the longer continuous coating is impossible. On the contrary, if the gelation time is too long, it takes a long time for foam curing.

(Foaming agent)
As the blowing agent, water and / or a low-boiling organic solvent such as cyclopentane or dichloromethane, a halogenated hydrocarbon, or the like is preferably used. Alternatively, a method in which air bubbles such as air and nitrogen are entrained in a polyol or prepolymer by a mechanical floss method or the like can be used.

The addition amount (mass basis) of the foaming agent varies depending on the density of the target foam (foamed urethane sheet), but 0.01 to 0.5 part of water and 100 parts of mechanical for 100 parts of the prepolymer having a terminal NCO group. In the floss method, nitrogen is about 10 to 600 cm ³ , and cyclopentane is about 0.05 to 2 parts.
As the foaming agent used in the present invention, water is particularly preferable because water easily dissolves the catalyst used in the present invention.

(Foam stabilizer)
In the present invention, a foam stabilizer may be blended. As the foam stabilizer, a silicone compound represented by a copolymer of polydimethylsiloxane and polyoxyalkylene polyol is preferably used. A hydroxyl-terminated polyether-modified silicone foam stabilizer may be used.
The amount of the foam stabilizer added is preferably 0.1 to 2.0 parts by mass with respect to 100 parts of the prepolymer having a terminal NCO group.

(Chain extender)
As a chain extender, for example, an aromatic diamine such as 4,4′-diamino-3,3′-dichlorodiphenylmethane (MOCA), which is generally used in the production of urethane sheets, has a high thickening speed and can be used without any catalyst. Even when a small amount of a catalyst is added, regardless of the type, it is easy to gel and cannot be continuously applied.

On the other hand, if a low molecular polyol is used as a chain extender, continuous coating for a long time is possible.
The molecular weight of the low molecular weight polyol used as a chain extender in the present invention is 500 or less. For example, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, glycerin, trimethylolpropane Examples include ethylene oxide adducts, ethylene oxide or propylene oxide adducts of bisphenol A, and ethylene oxide adducts of hydroquinone and resorcin.
Of these, low molecular weight polyols having a molecular weight of 200 or less and primary alcohols, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, hydroquinone, resorcin ethylene oxide adducts, and the like are particularly preferable. In addition, when bifunctional and trifunctional low molecular polyols are used in combination, cross-linking is introduced and restoration properties are improved, and a foam having a closed cell structure is easily obtained. Therefore, the target foamed polyurethane sheet has a closed cell structure. It is suitable when low water absorption is required.
Along with the low molecular weight polyol, a high molecular weight polyol having a molecular weight of over 500 is used in combination as a diluent for small components such as low molecular weight polyols and catalysts, so that it can be used as a meter for improving the raw material pump and as a reactivity regulator. It doesn't matter. As these polymer polyols, the same polyols as those used in the prepolymer described above can be used. In this case, the number of functional groups may be 2 to 4, and the molecular weight may be 500 to 6000.

  The blending amount of the low molecular polyol with respect to 100 parts of the prepolymer having a terminal NCO group is preferably 0.9 to 1.2 in terms of an equivalent ratio of NCO group / OH group including the OH group of water used as a blowing agent.

(Organic acid with a pKa of 3.46 to 1.00)
Examples of the organic acid having a pKa of 3.46 to 1.00 used in the present invention (pKa in the parentheses below) include m-phthalic acid (3.46), o-phthalic acid (2.95), citric acid ( 3.09), fumaric acid (3.03), malonic acid (2.83), trimellitic acid (2.52), o-nitrobenzoic acid (2.17), maleic acid (1.93), dichloro Examples include acetic acid (1.29), oxalic acid (1.23), and dihydroxyfumaric acid (1.14).

Orthophthalic acid, malonic acid, maleic acid, fumaric acid and dichloroacetic acid are preferred because they are easily dissolved in urethane raw materials among acids of pKa 3.46 to 1.00, and orthophthalic acid is preferred because reactivity is easily controlled. It is particularly preferred to use maleic acid or malonic acid.
The addition amount of the organic acid having a pKa of 3.46 to 1.00 is 0.000 with respect to 100 parts of the prepolymer having a terminal NCO group, from the viewpoint of the amount required to neutralize the addition of the heterocyclic tertiary amine used together. It is preferable that it is 01-0.3 mass part.

(Heterocyclic tertiary amine)
The heterocyclic tertiary amine used in the present invention is a compound containing nitrogen in the cyclo ring. As the N-alkylimidazole, 1,2-dimethylimidazole, 1-isobutyl-2-methylimidazole, tris having a triazine ring ( Dimethylaminopropyl) hexatriazine, 1,4-diazabicyclo (2.2.2) octane having a dicyclo ring (triethylenediamine, abbreviated as TEDA), cycloamidine-based 1,8-diazabicyclo (5.4.0) undecene Representative examples include -7-ene (abbreviated as DBU) and 1,5-diazabicyclo (4.3.0) nonen-5-ene (abbreviated as DBN).
Among these heterocyclic tertiary amines, cycloamidine-based DBU and DBN and dicyclooctane-based TEDA are preferable because they have a high reaction rate at high temperatures and can shorten the solidification time.
The addition amount of the heterocyclic tertiary amine is preferably 0.01 to 0.3 parts by mass with respect to 100 parts of the prepolymer having a terminal NCO group from the viewpoint of accelerating the solidification reaction.

  Heterocyclic tertiary amine and the above-mentioned acid of pKa 3.46 to 1.00 may be blended separately in water, which is a low molecular polyol or a foaming agent, at approximately equivalent amounts, such as dimethylformamide and methylpyrrolidone. You may melt | dissolve in a polar solvent and mix with a urethane raw material, and you may mix | blend as a salt by mixing an acid and an amine by a substantially equivalent beforehand. A heterocyclic tertiary amine and an acid having a pKa of 3.46 to 1.00 can promote a rapid solidification reaction by increasing the temperature while effectively suppressing the initial reaction in the composition of the present invention.

In order to make a salt from a heterocyclic tertiary amine and an acid having a pKa of 3.46 to 1.00, the amine and the acid are mixed in an equimolar amount, or, for example, ethylene glycol or 1,4-butanediol, The method of mixing and reacting in dipropylene glycol or in a polar solvent such as water, dimethylformamide, or methylpyrrolidone can form a solution even in the case of a salt that is difficult to dissolve.
When the acid of pKa 3.46 to 1.00 and the heterocyclic tertiary amine are blended as a salt, the addition amount (mass basis) is 0.02 to 0.5 part with respect to 100 parts of the prepolymer. From the physical properties, it is particularly preferably 0.1 to 0.3 part.

  Next, the process for producing a foamed polyurethane sheet using the reaction stock solution will be specifically described with reference to the accompanying drawings.

  FIG. 1 schematically shows an example of a device configuration for carrying out the method for producing a foamed polyurethane sheet of the present invention. A foamed polyurethane sheet manufacturing apparatus 100 shown in FIG. 1 includes a first web roll 14 that unwinds a first continuous web 14A, a coating apparatus 12 that coats a reaction stock solution on the first continuous web 14A, and a first web roll 14. A large-diameter roller 18 that guides the unwound first continuous web 14A directly below the coating device 12, a second web roll 16 that unwinds the second continuous web 16A, and a second continuous web 16A as the first continuous web. The guide roller 20 guided onto the coating film 10 on 14A and the reaction film 10 coating film 10 sandwiched between the two continuous webs 14A and 16A are guided to the heating device 22 and heated and cured by the heating device 22 to be cured. Conveying rollers 28A and 28B for conveying the urethane sheet 30 and the continuous webs 14A and 16A separated from the foamed urethane sheet 30 are wound up and collected. And a recovery roller 24.

<Application process>
First, a reaction stock solution obtained by mixing and stirring raw material components, that is, a prepolymer having a terminal NCO group derived from MDI, a foaming agent, a low molecular polyol having a molecular weight of 500 or less, an organic acid having a pKa of 3.46 to 1.00, and a heterocyclic ring 3 A reaction stock solution in which a primary amine (or an organic acid having a pKa of 3.46 to 1.00 and a salt of a heterocyclic tertiary amine) is mixed is continuously applied onto the first continuous web 14A to form the coating film 10.

  The reaction stock solution used in the production of the foamed urethane sheet of the present invention can be applied continuously because the initial reaction of urethanization is suppressed and the thickening is suppressed even at a temperature of about 40 to 70 ° C. If the liquid temperature is further increased by 20 to 50 ° C to 90 to 120 ° C, the reaction rate becomes rapid, so the solidification reaction is completed quickly, and long foamed urethane sheet products are wound around paper tubes or cut into short pieces. It becomes possible to do.

For example, a resin film or a paper body is preferably used as the first continuous web 14.
The resin film is not particularly limited as long as it is not deformed by application of the reaction stock solution and heating in the heating step, but from the viewpoint of resistance to the reaction stock solution, heat resistance, etc., a film of polyester, polypropylene, polymethylpentene or the like is preferable. .
If necessary, the surface of the resin film may be subjected to corona discharge treatment, plasma treatment or the like to improve the adhesion to the urethane foam sheet.

Moreover, after manufacturing a foaming urethane sheet, you may use the resin film in which the surface which forms the coating film of a reaction undiluted | stock has releasability so that a resin film may be peeled easily.
As a resin film having releasability, a method of applying a silicone release agent on one side of a resin film, a method of using a resin film having releasability such as polypropylene resin or polymethylpentene resin as it is, and having releasability There is a method of laminating a resin film on a polyester film or the like.

When a paper body is used as the first continuous web 14A, a glassine paper or a high-quality paper whose surface is coated with polyethylene or polypropylene, or a resin coated with a silicone release agent is used.
As the first continuous web 14A used in the present invention, a resin film or a releasable resin film is preferable because the solidification speed of the foam is high and the thickness accuracy is high.

  As the coating device 12 for coating the reaction stock solution on the first continuous web 14A, it is preferable to use a die coater, a roll coater, a knife coater, a comma coater, or the like. The reaction stock solution is stirred with a mixing device, discharged from a discharge nozzle with a traverse (repetitive coating) device and thinly coated with a roll coater or knife coater, or the reaction stock solution is introduced into a die coater from the discharge nozzle onto a continuous web. A coating method is also preferable.

  Although the thickness of the coating film 10 may be determined according to the intended use of the foam, it is preferably 0.1 to 20 mm from the viewpoints of the foaming ratio of the foamed urethane sheet and the desired thickness.

<Second continuous web supply process>
The second continuous web 16A is supplied to the coating film 10 on the first continuous web 14A, and the coating film 10 is sandwiched between the two continuous webs 14A and 16A.
As the second continuous web 16A, the resin film or paper exemplified in the description of the first continuous web 14A can be used. In addition, at least one continuous web of the first continuous web 14 </ b> A and the second continuous web 16 </ b> A is in contact with the coating film 10 from the viewpoint of easily peeling at least one continuous web of the urethane foam sheet 30 after the heating step. It is preferable to use a continuous web whose surface has releasability.

  The second continuous web 16A is continuously unwound from the second web roll 16 around which the second continuous web 16A is wound, and is placed on the coating film 10 on the first continuous web 14A. As a result, the coating film 10 is sandwiched between the two continuous webs 14A and 16A.

  The apparatus shown in FIG. 1 is configured so that the coating film 10 is sandwiched between two continuous webs 14A and 16A. However, after the coating film is formed on the first continuous web 14A, the second continuous web is formed. You may advance to the next heating process, without covering 16A.

<Heating process>
The coating film 10 is conveyed into the heating device 22 while being sandwiched between two continuous webs 14A and 16A and cured by heating.
The heating temperature for curing is preferably 90 to 120 ° C., and is preferably solidified at a temperature in this range in 5 to 20 minutes.
As the heating device 22, an infrared heater, an electric heater, a gas combustion furnace, or the like can be used.

  If the time until the coating film 10 is solidified (cured) can be shortened, the reaction stock solution can be applied at high speed, and co-washing with the fresh raw material of the coating apparatus 12 is promoted, which is very advantageous for long-time coating. .

<Peeling process>
The foamed urethane elastomer (foamed urethane sheet) 30 foamed and cured by a heating process may be wound while the continuous webs 14A and 16A are in close contact with the foamed urethane sheet 30, or the continuous webs 14A and 16A are releasable. In the case of a web, as shown in FIG. 1, the releasable web is peeled off from the foamed urethane sheet 30 and wound around the collection rollers 24 and 26 to be collected. The collected continuous webs 14A and 16A can be reused as the supply rolls 14 and 16.

Through the above steps, it is possible to continuously produce a long foamed urethane sheet having a high density of about 0.2 to 0.95 g / cm ³ and high mechanical strength with little variation in quality.

The foamed urethane sheet produced in the present invention has a closed-cell structure or an open-cell structure, and can be used to produce a foamed urethane sheet for applications that require toughness and durability, such as polishing pads and damping pads for railways. Even if it exists, this invention is applicable.
The method for producing a foamed urethane sheet of the present invention is particularly suitable for the production of a vibration damping pad for railways and a building / civil engineering structure that is easy to increase the closed cell ratio and requires a low water absorption rate. Applicable.
Furthermore, according to the present invention, the foamed urethane sheet can be continuously produced, so that the variation in quality is extremely small and, of course, the yield is greatly improved as compared with those produced and batch-processed.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, “part” and “%” relating to the blending amount (content, addition amount) are based on mass.

(Raw materials used)
The raw material used by the Example and the comparative example is demonstrated.

[Terminal NCO group prepolymer]
PP-A: 100 parts of PTMG-1000 (Mitsubishi Chemical Polyoxytetramethylene glycol, molecular weight 1000) and 50 parts of Pure MDI (Nippon Polyurethane Diphenylmethane Diisocyanate) are mixed and reacted at 70 ° C. for 2 hours. Thus, an NCO group-terminated prepolymer having an NCO% of 5.25% was obtained.

  PP-B: 100 parts of PTMG-1000 and 95.1 parts of pure MDI were mixed and reacted at 70 ° C. for 2 hours to obtain an NCO group-terminated prepolymer having an NCO% of 9.2%.

  PP-C: 100 parts of PTMG-1000 and 31.68 parts of T-80 (Toluene diisocyanate manufactured by Nippon Polyurethane Co., Ltd.) are mixed and reacted at 80 ° C. for 3 hours to give an NCO group of 5.25% NCO%. A terminal prepolymer was obtained.

(Chain extender)
14BD: 1,4-butanediol TMP: trimethylolpropane MOCA: 4,4′-diamino-3,3′-dichlorodiphenylmethane

[Foaming agent]
Water or nitrogen

[Foam stabilizer]
NP-100: Hydroxyl-terminated polyether-modified silicone foam stabilizer (manufactured by Shin-Etsu Chemical Co., Ltd.)

〔catalyst〕
In CA: dimethylformamide, 1,4-diazabicyclo (2.2.2) octane (TEDA) and maleic acid were mixed at 11.2: 11.6 (mass ratio) at room temperature to obtain catalyst salt CA. A 50% solution was obtained.

  CB: TEDA and o-phthalic acid were mixed at 11.2: 16.6 (mass ratio) in dimethylformamide to obtain a 50% solution of catalyst salt CB.

  CC: 1,8-diazabicyclo (5.4.0) undecene-7 (DBU) and maleic acid were mixed in 15.2: 5.8 (mass ratio) in dimethylformamide to obtain catalyst salt CC 50 % Solution was obtained.

[Resin film]
Film A: A polyester film having a thickness of 100 μm coated with a releasable silicone resin with a thickness of 0.3 μm on one side.

Example 1
100 parts PP-A, 5.62 parts 14BD, 0.05 parts water, 0.5 parts NP-100, 0.15 parts dimethylformamide (1/1) solution of TEDA, maleic acid A premix with a dimethylformamide (1/1) solution at a ratio of 0.15 parts was charged into the tank, and conveyed to a mixing head with a metering pump and mechanically stirred.

  The stirred reaction stock solution was coated on a polyester film (film A) subjected to a release treatment using a die coater to a thickness of 1 mm, and another release film (film A) from the top was subjected to a release treatment to form a coating solution. Covered to face. This continuous coated product was heated in an oven at 100 ° C. to observe the foam curing time, and after solidifying, the film A on both sides was peeled off to obtain a foamed urethane sheet having a thickness of about 2 mm.

[Gelification time]
The gelation time was measured as the time for the viscosity to reach 40,000 Pa · s at 70 ° C. by mixing a prepolymer having terminal NCO groups derived from MDI with a predetermined amount of chain extender and catalyst.

[Solidification time]
The solidification time is that after a predetermined reaction stock solution is applied on a resin film having releasability, the same releasable resin film is placed on the upper surface of the coating film, and the resin film is solidified by heating at 100 ° C. It was set as the time which can peel a film.

[Gelification / solidification ratio]
From the gelation time (seconds) and the solidification time (minutes) measured as described above, the ratio (gelation time (seconds) / solidification time (minutes)) was determined. The larger the gelation / individualization ratio, the easier it is to apply the reaction stock solution continuously.

[Continuous coating]
Judgment of the continuous coating time was measured by observing whether the reaction stock solution was gelled and streaks were formed in the coated product in the die coater or the thickness was abnormal.

〔density〕
The density of the obtained urethane foam sheet was measured by dividing the weight of the sample by the volume.

[Self-bubble rate]
The closed cell ratio of the obtained urethane foam sheet was measured with a Beckman air comparison hydrometer 930 type (manufactured by Tokyo Science) based on ASTM D2856.

[Water absorption rate]
The water absorption of the obtained urethane foam sheet was measured by weight% obtained by submerging the sample under a depth of 10 cm and dividing the weight increase after 24 hours by the weight before the test.

[A hardness]
The hardness A of the obtained urethane foam sheet was measured by a value immediately after pressing the sample surface with a JIS-A hardness meter.

〔Comprehensive judgment〕
The obtained foamed urethane sheet was comprehensively evaluated according to the following criteria.
AA: A composition in which continuous coating is possible for 2 hours or more and a closed cell rate is 80% or more A: A composition in which continuous coating is 2 hours or more but the closed cell rate is less than 80%
B: Composition with continuous coating of 1 to 1.5 hours C: Composition with continuous coating of 0.5 hours or less

(Example 2)
A foamed urethane sheet was obtained in the same manner as in Example 1 except that 0.3 part of CA was used as the catalyst.

(Example 3)
A urethane foam sheet was obtained in the same manner as in Example 1 except that 0.3 part of CB was used as the catalyst.

Example 4
A urethane foam sheet was obtained in the same manner as in Example 1 except that 0.3 parts of CC was used as the catalyst.

(Example 4 ')
A foamed urethane sheet was obtained in the same manner as in Example 4 except that the foam stabilizer was not used.

(Example 5)
Example 1 except that 100 parts of PP-B, 9.87 parts of 14BD, 0.08 part of water, 0.5 part of NP-100, and 0.3 part of catalyst CC were used for the prepolymer. A foamed urethane sheet was obtained by this method.

(Example 6)
A urethane foam sheet was obtained in the same manner as in Example 5 except that 7.40 parts of 14BD and 2.47 parts of TMP were used as chain extenders.

(Example 7)
A foamed urethane sheet was obtained in the same manner as in Example 5, except that 4.93 parts of 14BD and 4.93 parts of TMP were used as the chain extender.

(Example 8)
A solution mixed in the same manner as in Example 2 except that water as a blowing agent was removed was introduced into an Oaks mixer), and a reaction stock solution in which 100 cm ³ of nitrogen was mechanically entrained as foam with respect to 100 cm ^{3 of} the urethane raw material. The foamed urethane sheet was obtained by applying onto the film A using a die coater in the same manner as in Example 1.

  The foamed polyurethane theta produced in Examples 2 to 8 was also evaluated in the same manner as in Example 1. Table 1 below shows the composition and evaluation results of the reaction stock solution used in the production of the urethane foam sheet in the examples. In addition, a blank represents that it is not mix | blended.

(Comparative Example 1)
The experiment was conducted in the same manner as in Example 1 except that 0.1 part of 1,4-diazabicyclo (2.2.2) octane (TEDA) was used as the catalyst, but the gelation time was too early as 30 seconds. Continuous coating was not possible at all.

(Comparative Example 2)
The experiment was conducted in the same manner as in Example 1 except that 16.68 parts of MOCA was used as a chain extender and 0.3 part of catalyst CC was added. The gelation time was as fast as 60 seconds and the solidification time was 5 minutes. The continuous coating time was as short as about 10 minutes.

(Comparative Example 3)
The experiment was performed in the same manner as in Example 3 except that PP-C was used as the prepolymer. The gelation time was as long as 300 seconds, but since the solidification time was as long as 30 minutes, the coating speed could not be increased, and gelation occurred in the die coater, and the continuous coating time was as short as about 10 minutes. Furthermore, the obtained urethane foam sheet had an A hardness of 20, and only a soft one was obtained.

(Comparative Example 4)
The experiment was conducted in the same manner as in Comparative Example 3 except that 16.68 parts of chain extender and 0.3 part of catalyst CC were used. However, since gelation time was as short as 60 seconds, continuous coating was completely impossible. There wasn't.

(Comparative Example 5)
The experiment was performed in the same manner as in Comparative Example 4 except that the amount of catalyst CC added was 0.1 part. The gelation time was extended to 200 seconds, but the solidification time was as long as 20 minutes, so the continuous coating time was 10 minutes.

  Table 2 below shows the composition and evaluation results of the reaction stock solution used in the production of the urethane foam sheet in the comparative example.

  The foamed urethane sheet produced by the present invention has an open-cell structure or closed-cell structure, and has elastic recovery and mechanical strength, and is a polishing pad that precisely polishes semiconductor wafers, glass substrates for displays, etc. It is also suitably applied to applications that require extremely high durability, such as anti-vibration pads that prevent noise and vibration generated from railway tracks, or anti-vibration pads that are used in automobiles, construction, civil engineering, and the like.

DESCRIPTION OF SYMBOLS 10 Coating film 12 Coating apparatus 14 1st web roll 14A 1st continuous web 16 2nd web roll 16A 2nd continuous web 18 Large diameter roller 22 Heating device 24 1st collection roll 26 2nd collection roll 30 Foam urethane sheet 100 Foamed urethane sheet manufacturing equipment

Claims (4)

A reaction stock solution in which a prepolymer having a terminal NCO group derived from diphenylmethane diisocyanate, a blowing agent, a low molecular polyol having a molecular weight of 500 or less, an organic acid having a pKa of 3.46 to 1.00, and a heterocyclic tertiary amine are mixed, or , A prepolymer having a terminal NCO group derived from diphenylmethane diisocyanate, a blowing agent, a low molecular polyol having a molecular weight of 500 or less, and a salt of an organic acid having a pKa of 3.46 to 1.00 and a heterocyclic tertiary amine A coating step of continuously coating the reaction stock solution on the first continuous web to form a coating film;
A heating step of heating and curing the coating film on the first continuous web;
A method for producing a foamed urethane sheet. After the coating process, before the heating process, a second continuous web is supplied to the coating film on the first continuous web and the coating film is sandwiched between the two continuous webs. Including the supply process,
The method for producing a urethane foam sheet according to claim 1, wherein the heating step is a step of heating and curing the coating film in a state of being sandwiched between the two continuous webs.   The method for producing a urethane foam sheet according to claim 2, wherein at least one of the first continuous web and the second continuous web is a continuous web having a releasable surface in contact with the coating film. The organic acid having a pKa of 3.46 to 1.00 is orthophthalic acid, maleic acid, or malonic acid, and the heterocyclic tertiary amine is a cycloamidine type or a dicyclooctane type. The manufacturing method of the urethane foam sheet of Claim 1.