Method for preventing foaming of two component polyurethane composition and two component polyurethane composition

Abstract

To provide a method that can suppress foaming during curing of a two-component polyurethane composition more effectively than conventional methods and can produce a cured product having desired physical properties, and a two-component polyurethane composition that can be used in the method.SOLUTION: There is provided a method for preventing foaming during curing of a two-component polyurethane composition having a first component containing a polyol and a second component containing a polyisocyanate, the method comprising the steps of preparing the first component and the second component, mixing the first component and the second component, and adding a defoamer and a foam inhibitor to the first component, the second component or a mixture thereof, wherein the polyol is an ester of a fatty acid and a polyhydric alcohol, the defoamer is an olefin polymer, the foam inhibitor is an organic carboxylic acid, and the foam inhibitor is present in an amount of 1.0 to 5.0 pts.mass based on 100 pts.mass of the first component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for preventing foaming during curing of a two-component polyurethane composition, and to a two-component polyurethane composition that can be used in the method. [Background technology]

[0002] Polyurethane compositions are widely used in adhesive, sealant, and coating applications, with two-component polyurethane compositions offering advantages over one-component polyurethane compositions in terms of rapid strength development and a wide range of in-use mechanical properties, from viscoelastic to highly structured.

[0003] An example of a two-component polyurethane composition used for such applications is disclosed in Patent Document 1. Patent Document 1 discloses a two-component polyurethane composition composed of a polyol, a polyisocyanate, a blocked amine, a metal catalyst, and the like. The two-component polyurethane composition of Patent Document 1 is thought to be intended to use a blocked amine to extend the usable life of the two-component polyurethane composition and enable it to cure without generating bubbles to form an elastic material with high strength.

[0004] Meanwhile, Patent Document 2 discloses a two-component polyurethane sealant containing a base agent made of a urethane prepolymer, a polyol having a molecular weight within a predetermined range, a curing catalyst made of an organic carboxylic acid metal salt, a carboxylic acid that functions as a stabilizer for the curing catalyst, and a curing agent that includes a plasticizer, etc. In addition to reducing the amount of plasticizer contained, the sealant in Patent Document 2 is thought to be intended to solve problems that curing catalysts have, such as catalyst deactivation under high humidity conditions and priority given to the reaction between moisture and isocyanate.

[0005] However, the present inventors have recognized that there is room for further improvement, since the cured products obtained by curing these conventional two-component polyurethane compositions may contain minute bubbles or may not necessarily have sufficient physical properties such as tensile strength. Furthermore, the present inventors have recognized that there is room for further improvement so that foaming of two-component polyurethane compositions can be prevented while ensuring that such desired physical properties are not impaired, since compositional changes to suppress foaming may impair the desired physical properties that the two-component polyurethane composition should inherently possess. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2015-534590 [Patent Document 2] Patent No. 3696447 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a method that can suppress foaming during curing of a two-component polyurethane composition more than conventional methods and can form a cured product having desired physical properties, and a two-component polyurethane composition that can be used in this method. [Means for solving the problem]

[0008] In order to achieve the above object, in one embodiment, the present invention has the following configuration. [1] A method for preventing foaming during curing of a two-component polyurethane composition having a first component containing a polyol and a second component containing a polyisocyanate, comprising: The method comprises: preparing the first agent and the second agent; mixing the first part and the second part; adding a defoaming agent and a foam inhibitor to the first part, the second part, or a mixture thereof; the polyol is an ester of a fatty acid and a polyhydric alcohol, the antifoaming agent is an olefin polymer; The foam inhibitor is an organic carboxylic acid, The method, wherein the foam inhibitor is present in an amount of 1.0 to 5.0 parts by mass relative to 100 parts by mass of the first agent. [2] The method according to [1], wherein the polyisocyanate is an isocyanate oligomer. [3] The method according to [1] or [2], wherein the fatty acid is mainly ricinoleic acid. [4] The method according to any one of [1] to [3], wherein the organic carboxylic acid has a branched alkyl group. [5] [1] A step of preventing foaming of the two-component polyurethane composition by the method described in [1]; forming a waterproof coating film using the two-component polyurethane composition; A method for producing a waterproof coating film, comprising: [6] A two-component polyurethane composition having a first component containing a polyol and a second component containing a polyisocyanate, The first agent or the second agent further contains a defoaming agent and a foam inhibitor, The antifoaming agent is a nonionic olefin polymer, The foam inhibitor is an organic carboxylic acid, The foam inhibitor is contained in an amount of 1.0 to 5.0 parts by mass relative to 100 parts by mass of the first part in a two-part polyurethane composition. [Effects of the Invention]

[0009] The method and composition of the present invention can suppress foaming during curing of a two-component polyurethane composition more than conventional methods, and can form a cured product having desired physical properties. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a photograph of the surface of a cured product obtained by curing a two-component polyurethane composition prepared in a first test. [Figure 2] FIG. 1 is a photograph of the surface of a cured product obtained by curing a two-component polyurethane composition (containing an antifoaming agent and 0 to 7 parts by mass of a foam inhibitor per 100 parts by mass of the first component) prepared in the second test.

[0011] The present invention will be described in detail below. The two-component polyurethane composition has a first component containing a polyol and a second component containing a polyisocyanate. A defoaming agent and a foam inhibitor are added to the first component, the second component, or a mixture of the first component and the second component.

[0012] In this specification, polyol refers to a compound (polyhydric alcohol) having two or more active hydrogen groups (preferably hydroxyl groups). Polyisocyanate refers to a compound having two or more isocyanate groups. Polyurethane refers to a compound in which a polyol and a polyisocyanate are bonded via a urethane bond.

[0013] "Molecular weight" is understood herein to mean the molar mass (g / mol) of a molecule. "Average molecular weight" means the number average Mn of an oligomeric or polymeric mixture of molecules, usually determined by gel permeation chromatography (GPC) against polystyrene as standard. "Room temperature" herein means a temperature of 23°C.

[0014] As used herein, a specific component being a "major component" means that the specific component is present in an amount of 50% by mass or more, based on 100% by mass of all components in the agent containing the specific component. In another preferred embodiment, the specific component may be present in an amount of 70% by mass or more, based on 100% by mass of the agent containing the specific component.

[0015] [Polyol] The polyol contained as a component of the first agent may be a commercially available polyol or a mixture of multiple commercially available polyols. The polyol may be, for example, a fat or oil having a hydroxyl group, a polyether polyol, a polyester polyol, a (meth)acrylic polyol, a polybutadiene polyol, a hydrogenated polybutadiene polyol, a low-molecular-weight polyhydric alcohol, or a mixture thereof.

[0016] The polyol is more preferably an ester of a fatty acid and a polyhydric alcohol. The ester may be an ester of a fatty acid having a hydroxyl group and a polyhydric alcohol, such as an ester of ricinoleic acid and glycerin, or may be an ester in which a hydroxyl group is introduced into a vegetable oil or fat having no hydroxyl group by chemical reaction. The polyol is even more preferably an ester of a fatty acid having a hydroxyl group and a polyhydric alcohol.

[0017] The "fatty acid having a hydroxyl group" preferably has ricinoleic acid as a main component. More preferably, ricinoleic acid accounts for 80% by mass or more of the fatty acids constituting the polyol (100% by mass). In castor oil, approximately 90% of the fatty acids constituting the molecule are ricinoleic acid. Therefore, castor oil can be used as a polyol composed of a fatty acid having ricinoleic acid as a main component.

[0018] Preferred vegetable oils and fats that do not have hydroxyl groups include those with an iodine value of 100 or more, such as linseed oil, safflower oil, soybean oil, tung oil, poppy seed oil, rapeseed oil, sesame oil, rice bran oil, tall oil, cottonseed oil, and corn oil. Of these, soybean oil is preferred. For a method of adding hydroxyl groups to vegetable oils and fats that do not have hydroxyl groups using a chemical reaction, see, for example, JP 2005-320431 A.

[0019] The castor oil may be unmodified castor oil or modified castor oil. The castor oil is preferably unmodified castor oil. Unmodified castor oil is extracted from castor seeds (Ricinus communis, Euphorbiaceae) and purified, and is not crosslinked (modified) with a dibasic acid or the like. The castor oil is preferably dehydrated.

[0020] Modified plant-derived oils, such as modified castor oil, are prepared by mixing a dibasic acid and a plant-derived oil to achieve the desired properties and then subjecting them to a dehydration-condensation reaction. Known methods can be used to synthesize these modified plant-derived oils. For example, a plant-derived oil is dissolved in a solvent and then a dibasic acid is added. The reaction mixture is refluxed using a Dean-Stark trap, and the resulting water is removed from the system during the dehydration-condensation reaction. After the reaction is complete, the solvent is removed under reduced pressure to obtain the desired compound.

[0021] The polyol preferably has an average functionality of 1.5 to 5.0, 2.0 to 4.0, and particularly preferably 2.5 to 3.5.

[0022] The polyol preferably has a hydroxyl value of 120 to 200 mgKOH / g, 140 to 180 mgKOH / g, or 156 to 165 mgKOH / g.

[0023] The polyol preferably has an iodine value of 60 to 110 gI2 / 100 G. The iodine value is preferably 70 to 100 gI2 / 100 G, and more preferably 80 to 90 gI2 / 100 G.

[0024] The polyol preferably has secondary hydroxyl groups because it has a suitable reactivity with isocyanate groups, and it is preferable that the majority of the hydroxyl groups in the polyol are secondary hydroxyl groups.

[0025] The polyol is preferably present in an amount of 60 wt-% to 100 wt-%, preferably 80 wt-% to 99.7 wt-%, more preferably 95 wt-% to 99.5 wt-%, based on the total weight of the first part.

[0026] [Polyisocyanate] The polyisocyanate contained in the second agent is a compound having two or more isocyanate groups. The polyisocyanate is preferably an isocyanate oligomer, more preferably an isocyanurate (trimer), and even more preferably an isocyanurate of an aliphatic diisocyanate. The aliphatic diisocyanate is a compound having a structure in which two isocyanate groups are bonded to an aliphatic hydrocarbon. The aliphatic hydrocarbon group may be, for example, linear, branched, cyclic, or a combination thereof.

[0027] The diisocyanates that make up the above polyisocyanates are toluene diisocyanate (TDI), diphenylmethane diisocyanate (unsubstituted MDI, also known as pure MDI or monomeric MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), tolidine diisocyanate (TODI), 1,5-naphthalene diisocyanate (NDI), triphenylmethane triisocyanate, and polymeric MDI (diphenylmethane diisocyanate (pure MDI) polymerized to a high molecular weight). aromatic polyisocyanates such as methyl methyl ether (MDI) and modified MDI; or aliphatic polyisocyanates such as pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, norbornane diisocyanate (NBDI), transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (H6XDI), and dicyclohexylmethane diisocyanate (H12MDI). Of these, the diisocyanate is preferably an aliphatic polyisocyanate, and more preferably HDI.

[0028] The polyisocyanate is preferably present in an amount of 60 wt-% to 100 wt-%, preferably 80 wt-% to 100 wt-%, more preferably 95 wt-% to 100 wt-%, based on the total weight of the second part.

[0029] [catalyst] The two-component polyurethane composition preferably contains a catalyst for accelerating the urethane reaction between the polyol contained in the first component and the polyisocyanate contained in the second component. The catalyst can be present as a component of the first component and / or the second component, but is preferably present as a component of the first component. The catalyst may be a metal catalyst such as a bismuth-based catalyst or a tin-based catalyst. Specific examples of the catalyst include a bismuth-based catalyst such as bismuth trioctate and a tetravalent tin catalyst such as dioctyltin(IV) dilaurate. Among these, bismuth-based catalysts are preferred.

[0030] When the two-part polyurethane composition contains a metal catalyst, the metal catalyst is preferably contained in an amount of 0.001 to 2.0% by mass, and more preferably 0.01 to 1.0% by mass, relative to 100% by mass of the first part.

[0031] [Antifoaming agent] The two-component polyurethane composition of the present invention contains an antifoaming agent. The antifoaming agent is a component that is thought to function primarily to burst and eliminate air bubbles that become entrapped when the first and second components are stirred and mixed. The antifoaming agent may be contained in either the first or second component, but is preferably contained in the first component.

[0032] The antifoaming agent may be one that is commonly used in two-component polyurethane compositions. The antifoaming agent may be, for example, an acrylic polymer, a vinyl ether polymer, a butadiene polymer, an olefin polymer, a dimethyl silicone, or a modified silicone. Among these, the antifoaming agent is preferably an olefin polymer. The olefin polymer may be, for example, FLOWLEN AC-2200HF (Kyoeisha Chemical Co., Ltd.).

[0033] From the viewpoint of balancing foam suppression and various physical properties, the antifoaming agent is preferably present in an amount of 0.01 to 5.0 mass % relative to 100 mass % of the first part, more preferably 0.05 to 3.0 mass %, and even more preferably 0.1 to 1.0 mass %.

[0034] [Foam suppressor] The two-component polyurethane composition of the present invention contains a foam inhibitor, which is a component that is thought to inhibit the generation of carbon dioxide gas due to a side reaction by controlling the urethane curing reaction.

[0035] The foam inhibitor used in the two-component polyurethane composition of the present invention is preferably an organic carboxylic acid or a metal salt of an organic carboxylic acid, and more preferably an organic carboxylic acid.

[0036] The organic carboxylic acid is preferably an organic carboxylic acid having a branched alkyl group. The organic carboxylic acid preferably has 5 to 15 carbon atoms, more preferably 6 to 10 carbon atoms. Examples of such carboxylic acids that can be used include octylic acid, 2-ethylhexyl acid, and neodecanoic acid.

[0037] In order to balance the foam suppression and various physical properties, the foam inhibitor is preferably present in an amount of 0.1 to 6.0 mass % relative to 100 mass % of the first part, and more preferably 1.0 to 5.0 mass %.

[0038] The two-component polyurethane composition of the present invention may contain other optional components such as a plasticizer, a solvent, a filler, and the like.

[0039] The two-component polyurethane composition of the present invention, by using a combination of an antifoaming agent and a foam inhibitor, exhibits an excellent balance between foam suppression and various physical properties without the need for defoaming treatment such as by reducing pressure. Therefore, defoaming treatment such as by reducing pressure is not essential when curing the two-component polyurethane composition of the present invention. However, if necessary, defoaming treatment such as by reducing pressure may be performed on the cured product.

[0040] [Application] The cured product of the two-component polyurethane composition formed by the method of the present invention is widely used as an adhesive, sealant, and coating material, and is particularly preferably used as a waterproof coating. [Example]

[0041] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0042] <Preliminary test, comparison of polyether polyol and castor oil> In Reference Examples A and B, two-component polyurethane compositions containing the first and second parts shown in Table 1 below were prepared. The first and second parts were stirred for 1 minute using a stirring device (product name "RW20 Digital", manufactured by IKA Corporation) to obtain a mixture. This mixture was applied to the surface of a glass plate coated with Teradite release agent MO-7 (manufactured by Terada Co., Ltd.), and left to stand at room temperature for 24 hours to obtain a cured product. Note that in Reference Examples A and B, degassing treatment under reduced pressure was not performed.

[0043] [Table 1]

[0044] Details of each component shown in Table 1 are as follows: <First agent (hardening agent)> PPG T600: Polypropylene glycol, product name "Sanix GP-600", manufactured by Sanyo Chemical Industries, Ltd. Castor oil: Polyol, product name: URIC H-2315, manufactured by Ito Oil Mills Co., Ltd. Bismuth catalyst: Product name: K-KAT XK640, manufactured by Kusumoto Chemicals Co., Ltd. Defoamer: Olefin polymer defoamer (product name: Flowlen AC-2200HF, manufactured by Kyoeisha Chemical Co., Ltd.) Foam suppressant: Octylic acid Product name: "Octylic acid", manufactured by JNC Corporation Comparative foam inhibitor: calcium oxide (product name: CML#35, manufactured by Omi Chemical Industry Co., Ltd.) <Second agent (main agent)> HDI trimmer: Product name "Desmodur N3300", isocyanate derivative of hexamethylene diisocyanate, manufactured by Covestro AG

[0045] The physical properties shown in Table 1 were measured as follows. Tensile strength: Tensile strength specified in JIS A6021-2000 [N / mm 2 ] Elongation: Elongation at break as specified in JIS A6021-2000 [%] Tear strength: Tear strength specified in JIS A6021-2000 [N / mm] D hardness

[0046] Preliminary tests showed that the cured product of a two-component polyurethane composition containing castor oil as a curing agent was superior in all physical properties, including tensile strength, elongation, tear strength, and D hardness, to the cured product of a composition containing polypropylene glycol as a curing agent. However, the cured product of the two-component polyurethane composition containing castor oil exhibited surface tackiness (residual tack) and foaming, leaving room for improvement in these respects.

[0047] <Test 1: Evaluation of foam suppression and surface adhesion> [Preparation of Composition] In Reference Examples 1-1 to 2-4, the first and second parts of two-component polyurethane compositions were prepared containing the components shown in Table 2 below. The first and second parts of Reference Examples 1-1 to 2-4 were each stirred for 1 minute using a stirring device (product name "RW20 Digital", manufactured by IKA Corporation). In Reference Examples 1-1 to 2-4, degassing treatment under reduced pressure was not performed.

[0048] [Table 2] The contents in Table 1 are shown in mass %.

[0049] Details of each component shown in Table 1 are as follows: <First agent (hardening agent)> Castor oil (polyol): Product name: URIC H-2315, manufactured by Ito Oil Mills Co., Ltd. Bismuth catalyst: Product name: K-KAT XK640, manufactured by Kusumoto Chemicals Co., Ltd. Defoamer: Olefin polymer defoamer (product name: Flowlen AC-2200HF, manufactured by Kyoeisha Chemical Co., Ltd.) Foam suppressant: Octylic acid Product name: "Octylic acid", manufactured by JNC Corporation Comparative foam inhibitor: calcium oxide (product name: CML#35, manufactured by Omi Chemical Industry Co., Ltd.) <Second agent (main agent)> HDI trimmer: Product name "Desmodur N3300", isocyanate derivative of hexamethylene diisocyanate, manufactured by Covestro AG

[0050] The mixtures obtained in Reference Examples 1-1 to 2-4 were applied to a slate board coated with DS Primer Eco (a one-component urethane resin primer), and left to stand at room temperature for 24 hours to obtain cured products. The appearance of each cured product is shown in Figure 1.

[0051] [Evaluation of foam suppression] The cured products of Reference Examples 1-1 and 2-1, which did not contain either octylic acid (foaming inhibitor) or calcium oxide (comparative foaming inhibitor), were foamed and contained fine bubbles. The cured products of Reference Examples 1-2, 1-3, and 1-4, which contained calcium oxide (comparative foaming inhibitor) but not octylic acid (foaming inhibitor), did not visually detect fine bubbles in the cross section, but had wavy surfaces. Reference Examples 1-2, 1-3, and 1-4 suggested that calcium oxide was unable to completely prevent foaming. The cured products of Reference Examples 2-2 and 2-3, which contained octylic acid, visually showed less foaming than the cured products of Reference Examples 1-1 and 2-1, which did not contain octylic acid. Furthermore, the cured product of Reference Example 2-4 was transparent and smooth and showed the least foaming in this test. It was shown that increasing the amount of octylic acid reduced foaming. Adding 5 wt% octylic acid to the curing agent suppressed foaming the most.

[0052] [Evaluation of surface adhesion] The presence or absence of surface tackiness of each cured product was confirmed by touching it with a finger. The cured products of Reference Examples 1-2 to 1-4, which used calcium oxide (2 to 10 mass%), had strong surface tackiness. The cured products of Reference Examples 2-2 to 2-4, which contained 1 to 5 mass% octylic acid, did not exhibit surface tackiness. These results demonstrate that adding a predetermined amount of octylic acid as a foam inhibitor in addition to a conventional antifoaming agent is effective in inhibiting foaming and reducing surface tackiness (improving curability).

[0053] <Second test: Test on foam inhibitor content> The first and second parts were prepared in the same manner as in Test 1, except that the content of octylic acid was changed to 0 to 7 mass% relative to 100 mass% of the first part, and then cured to obtain cured products. The physical properties of these cured products were measured in the same manner as in Test 1. The results are shown in Table 3.

[0054] [Table 3]

[0055] These results show that when octylic acid is contained in an amount of 1 to 5 mass % relative to 100 mass % of the first agent, the coating has suitable physical properties for a waterproof coating.

[0056] Figure 2 shows photographs of the surfaces of the cured products prepared in the second test. When octylic acid was used at 0%, the cured products had a problem of cloudy, orange peel-like, non-smooth surfaces due to fine bubbles in the coating film. When 1% octylic acid was added, this problem was alleviated. When 3% or more octylic acid was added, the cured products had transparent, smooth surfaces, and this problem was resolved.

Claims

1. A method for preventing foaming during curing of a two-component polyurethane composition having a first component containing a polyol and a second component containing a polyisocyanate, comprising: The method comprises: preparing the first agent and the second agent; mixing the first part and the second part; adding a defoaming agent and a foam inhibitor to the first part, the second part, or a mixture thereof; the polyol is an ester of a fatty acid and a polyhydric alcohol, the antifoaming agent is an olefin polymer; The foam inhibitor is an organic carboxylic acid, The foam inhibitor is present in an amount of 1.0 to 5.0 parts by mass per 100 parts by mass of the first agent.

2. The method of claim 1 wherein the polyisocyanate is an isocyanate oligomer.

3. 2. The method of claim 1, wherein the fatty acids are primarily ricinoleic acid.

4. The method of claim 1 , wherein the organic carboxylic acid has a branched alkyl group.

5. inhibiting foaming of a two-part polyurethane composition by the method of claim 1; forming a waterproof coating film using the two-component polyurethane composition; A method for producing a waterproof coating film, comprising:

6. A two-component polyurethane composition having a first component containing a polyol and a second component containing a polyisocyanate, The first agent or the second agent further contains a defoaming agent and a foam inhibitor, The antifoaming agent is a nonionic olefin polymer, The foam inhibitor is an organic carboxylic acid, The foam inhibitor is contained in an amount of 1.0 to 5.0 parts by mass per 100 parts by mass of the first agent.

Images