JP7532700B1 - Method for preventing foaming of two-component polyurethane composition and two-component polyurethane composition - Google Patents

Abstract

[Problem] The present invention aims to provide a method for preventing foaming during curing of a two-component polyurethane composition, which can suppress foaming more than conventional methods and can obtain a cured product having desired physical properties, and a two-component polyurethane composition that can be used in the method. [Solution] 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 an antifoaming agent 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 antifoaming agent 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 parts by mass per 100 parts by mass of the first component. [Selected Figure] None

Description

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

Polyurethane compositions are widely used as adhesives, sealants, and coating materials. In particular, two-component polyurethane compositions offer advantages over one-component compositions in terms of rapid strength development and a wide range of mechanical properties, from viscoelasticity to high structure.

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. It is believed that the two-component polyurethane composition of Patent Document 1 is intended to use a blocked amine to extend the pot life of the two-component polyurethane composition and to enable it to cure without generating bubbles and form an elastic material with high strength.

On the other hand, Patent Document 2 discloses a two-component polyurethane sealant that contains a base agent made of a urethane prepolymer, a polyol having a molecular weight within a specified 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 contains 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 inactivation under high humidity conditions and priority given to the reaction between moisture and isocyanate.

However, the present inventors felt that there was room for further improvement, since the cured products obtained by curing these conventional two-component polyurethane compositions may have slight foaming or may not necessarily have sufficient physical properties such as tensile strength. Furthermore, the present inventors felt that there was room for further improvement so that foaming of two-component polyurethane compositions could be prevented while ensuring that such desired physical properties are not impaired, since changes to the composition to suppress foaming may impair the desired physical properties that the two-component polyurethane composition should inherently possess.

Special Publication No. 2015-534590 Patent No. 3696447

The object of the present invention is therefore to provide a method that can suppress foaming during curing of a two-component polyurethane composition more than ever before and can form a cured product with desired physical properties, and a two-component polyurethane composition that can be used in that method.

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 steps of:
The method comprises:
preparing the first agent and the second agent;
mixing the first part and the second part;
adding a defoamer 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 defoaming 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 weight per 100 parts by weight 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 composed of 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 comprises a defoamer and a foam inhibitor;
The antifoaming agent is a non-ionic 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.

The method and composition of the present invention can suppress foaming during curing of a two-part polyurethane composition more than ever before, and can form a cured product with desired physical properties.

1 is a photograph of the surface of a cured product obtained by curing the two-component polyurethane composition prepared in the first test. 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 a second test.

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 defoamer and a foam inhibitor are added to the first component, the second component, or a mixture of the first component and the second component.

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

"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, typically determined by gel permeation chromatography (GPC) against polystyrene as standard. "Room temperature" in this specification means a temperature of 23°C.

In this specification, a specific component being a "major component" means that the specific component is present in an amount of 50% by mass or more relative to 100% by mass of all components of 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 relative to 100% by mass of the agent containing the specific component.

[Polyol]
The polyol contained as a component of the first agent may be a commercially available polyol or a mixture of a plurality of 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.

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 has been introduced into a vegetable oil or fat having no hydroxyl group by a chemical reaction. The polyol is even more preferably an ester of a fatty acid having a hydroxyl group and a polyhydric alcohol.

The above-mentioned "fatty acid having a hydroxyl group" preferably has ricinoleic acid as a main component. It is more preferable that ricinoleic acid accounts for 80% by mass or more of the 100% by mass of the fatty acids constituting the polyol. About 90% of the fatty acids constituting the molecules of castor oil are ricinoleic acid. Therefore, castor oil can be used as a polyol composed of fatty acids with ricinoleic acid as the main component.

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

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 the seeds of castor beans (Ricinus communis, Euphorbiaceae) and purified, and is not cross-linked (modified) with dibasic acids or the like. The castor oil is preferably dehydrated.

Modified plant-derived oils such as modified castor oil are prepared by mixing a dibasic acid and a plant-derived oil to obtain the desired properties, and then carrying out a dehydration condensation reaction. A known method can be used to synthesize the modified plant-derived oil. For example, a plant-derived oil is dissolved in a solvent of choice, and then a dibasic acid is added. This reaction solution is refluxed using a Dean-Stark trap, and while carrying out the dehydration condensation reaction, the water generated by the reaction is removed outside the system. After the reaction is completed, the solvent is removed under reduced pressure to obtain the desired compound.

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

The polyol preferably has a hydroxyl value of 120 to 200 mg KOH/g. It preferably has a hydroxyl value of 140 to 180 mg KOH/g. It is preferable that the hydroxyl value is 156 to 165 mg KOH/g.

The polyol preferably has an iodine value of 60 to 110 gI ₂ /100 G. The iodine value is preferably 70 to 100 gI ₂ /100 G, and more preferably 80 to 90 gI ₂ /100 G.

The polyol preferably has secondary hydroxyl groups because it has a suitable reactivity with isocyanate groups. It is preferable that the majority of the hydroxyl groups in the polyol are secondary hydroxyl groups.

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

[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.

The diisocyanates constituting the polyisocyanate are toluene diisocyanate (TDI), diphenylmethane diisocyanate (unsubstituted MDI, also called 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, polymeric MDI (diphenylmethane diisocyanate (pure MDI) is polymerized to a high molecular weight. and aromatic polyisocyanates such as methyl ether, methyl ether compound), modified MDI, and the like; and 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(isocyanatemethyl)cyclohexane (HXDI), and dicyclohexylmethane diisocyanate (HMDI).
Of the above diisocyanates, aliphatic polyisocyanates are preferred, and HDI is more preferred.

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

[catalyst]
The two-component polyurethane composition preferably contains a catalyst for promoting the urethane reaction between the polyol contained in the first component and the polyisocyanate contained in the second component. The catalyst may 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. Specifically, the catalyst may be, for example, a bismuth-based catalyst such as bismuth trioctate, or a tetravalent tin catalyst such as dioctyltin (IV) dilaurate. Among these, a bismuth-based catalyst is preferred.

When the two-component polyurethane composition contains a metal catalyst, the metal catalyst is preferably present 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 component.

[Antifoaming agent]
The two-component polyurethane composition of the present invention contains an antifoaming agent. The antifoaming agent is a component that is considered to have the function of bursting and eliminating bubbles that are 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.

The above-mentioned defoaming agent may be one that is commonly used in two-component polyurethane compositions. The defoaming 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. Of these, the defoaming agent is preferably an olefin polymer. The olefin polymer may be, for example, FLOWLEN AC-2200HF (Kyoeisha Chemical Co., Ltd.).

From the viewpoint of the balance between foaming inhibition and various physical properties, the above-mentioned defoaming agent is preferably present in a content of 0.01 to 5.0% by mass relative to 100% by mass of the first agent. The above-mentioned defoaming agent is more preferably present in a content of 0.05 to 3.0% by mass, and even more preferably present in a content of 0.1 to 1.0% by mass.

[Foam Inhibitor]
The two-component polyurethane composition of the present invention contains a foam inhibitor. In the present invention, the foam inhibitor is a component that is considered to suppress the generation of carbon dioxide gas due to a side reaction by controlling the urethane curing reaction.

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.

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, and more preferably has 6 to 10 carbon atoms. Examples of such carboxylic acids that can be used include octyl acid, 2-ethylhexyl acid, and neodecanoic acid.

In order to balance foaming inhibition and various physical properties, the foam inhibitor is preferably present in an amount of 0.1 to 6.0% by mass relative to 100% by mass of the first agent, and more preferably in an amount of 1.0 to 5.0% by mass.

The two-component polyurethane composition of the present invention may contain other optional components such as plasticizers, solvents, and fillers.

The two-component polyurethane composition of the present invention uses a combination of an antifoaming agent and a foam inhibitor, and thus has an excellent balance between foam inhibition and various physical properties, even without defoaming treatment such as by reducing pressure. Therefore, when curing the two-component polyurethane composition of the present invention, defoaming treatment such as by reducing pressure is not essential. However, if necessary, defoaming treatment such as by reducing pressure may be performed on the cured product.

[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, but is particularly preferably used as a waterproof coating.

The present invention will be specifically explained below with reference to examples. However, the present invention is not limited to these examples.

<Preliminary test, comparison of polyether polyol and castor oil>
In Reference Examples A and B, a two-component polyurethane composition was prepared containing the first and second parts shown in Table 1 below. 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 allowed to stand at room temperature for 24 hours to obtain a cured product. Note that in Reference Examples A and B, degassing treatment by reduced pressure was not performed.

Details of each component shown in Table 1 are as follows.
<First agent (curing agent)>
PPG T600: Polypropylene glycol, product name "Sannix GP-600", manufactured by Sanyo Chemical Industries, Ltd. Castor oil: Polyol, product name: URIC H-2315, manufactured by Ito Oil Mills, 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 inhibitor: Octylic acid (trade name: "Octylic acid"), manufactured by JNC Corporation Comparative foam inhibitor: Calcium oxide (trade 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

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

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 had surface tack (residual tack) and foaming, leaving room for improvement in these respects.

<First test: Evaluation of foaming inhibition 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 with a stirrer (product name "RW20 Digital", manufactured by IKA Corporation). In Reference Examples 1-1 to 2-4, degassing treatment by reduced pressure was not performed.

表１の含有量は質量％で示されている。

The contents in Table 1 are shown in mass %.

Details of each component shown in Table 1 are as follows.
<First agent (curing 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 inhibitor: Octylic acid (trade name: "Octylic acid"), manufactured by JNC Corporation Comparative foam inhibitor: Calcium oxide (trade 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

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

[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 fine bubbles were contained in the cured products. The cured products of Reference Examples 1-2, 1-3, and 1-4, which contained calcium oxide (comparative foaming inhibitor) but did not contain octylic acid (foaming inhibitor), did not visually confirm fine bubbles in the cross section, but had wavy surfaces. Reference Examples 1-2, 1-3, and 1-4 suggested that calcium oxide could not 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. In this case, foaming was most suppressed by adding 5 wt % of octylic acid to the curing agent.

[Evaluation of surface adhesion]
The presence or absence of surface tackiness of each cured product was confirmed by touching each product with a finger. The cured products of Reference Examples 1-2 to 1-4 using calcium oxide (2 to 10 mass%) had strong surface tackiness. The cured products of Reference Examples 2-2 to 2-4 containing 1 to 5 mass% octylic acid did not show surface tackiness. From these results, it was found that adding a predetermined amount of octylic acid as a foaming inhibitor in addition to a conventional defoaming agent is useful for suppressing foaming and reducing surface tackiness (improving curability).

<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 the cured products were measured in the same manner as in Test 1. The results are shown in Table 3.

These results show that when octylic acid is present at 1-5% by mass relative to 100% by mass of the first agent, it has suitable physical properties for a waterproof coating.

Figure 2 shows photographs of the surfaces of the cured products prepared in the second test. When 0% octylic acid was used, the cured products had a problem of having a cloudy, orange peel-like, non-smooth surface 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 a transparent, smooth surface, and this problem was eliminated.

Claims (4)

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 steps of:
The method comprises:
preparing the first agent and the second agent;
mixing the first part and the second part;
adding a defoamer 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 defoaming agent is an olefin polymer,
The defoaming agent is present in an amount of 0.01 to 5.0 parts by mass relative to 100 parts by mass of the first agent,
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 relative to 100 parts by mass of the first agent ,
the two-component polyurethane composition contains a catalyst for promoting a urethane reaction between a polyol contained in the first component and a polyisocyanate contained in the second component,
the catalyst is a metal catalyst;
The method according to claim 1, wherein the metal catalyst is present in an amount of 0.001 to 2.0 parts by mass relative to 100 parts by mass of the first agent . the polyisocyanate is an isocyanate oligomer,
The fatty acid is mainly composed of ricinoleic acid,
The method of claim 1 , wherein the organic carboxylic acid has a branched alkyl group . Preventing foaming of a two-component polyurethane composition by the method of claim 1 or 2 ;
forming a waterproof coating film using the two-component polyurethane composition;
A method for producing a waterproof coating film comprising: 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 defoamer, a foam inhibitor, and the two-component polyurethane composition contains a catalyst for promoting a urethane reaction between the polyol contained in the first agent and the polyisocyanate contained in the second agent;
the catalyst is a metal catalyst;
The metal catalyst is present in an amount of 0.001 to 2.0 parts by mass relative to 100 parts by mass of the first agent,
The antifoaming agent is a non-ionic olefin polymer,
The defoaming agent is present in an amount of 0.01 to 5.0 parts by mass relative to 100 parts by mass of the first agent,
The foam inhibitor is an organic carboxylic acid.
the polyol is an ester of a fatty acid and a polyhydric alcohol,
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, forming a two-part polyurethane composition.

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