Urethane Adhesive Composition

Abstract

A two-part urethane adhesive composition includes a main agent containing a filler and a urethane prepolymer having an isocyanate group and formed from a polyisocyanate A and a polyol 1 with two to three hydroxy groups per molecule and a number-average molecular weight of ≥1800. Isocyanate group content in the main agent is ≥5 mass % of a main agent total content. The composition includes a curing agent containing a polyoxyalkylene polyol, a polyol 2, a urethanization reaction catalyst, a filler, and zeolite, the polyoxyalkylene polyol having two to three hydroxy groups per molecule and having a number-average molecular weight of ≥1800, the polyol 2 having two or more hydroxy groups per molecule and having a number-average molecular weight of ≤200. The urethanization reaction catalyst contains an organic tin catalyst, and an amine catalyst represented by Formula (1) or an amine catalyst blocked with an acid.

Claims

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15. A urethane adhesive composition being a two-part urethane adhesive composition comprising a main agent and a curing agent, wherein the main agent contains a urethane prepolymer and a filler, the urethane prepolymer having an isocyanate group and being formed from a polyisocyanate A and a polyol 1 that has two to three hydroxy groups per molecule and has a number-average molecular weight of not less than 1800, a content of isocyanate groups in the main agent is not less than 5 mass % of a total amount of the main agent, the curing agent contains a polyoxyalkylene polyol, a polyol 2, a urethanization reaction catalyst, a filler, and zeolite, the polyoxyalkylene polyol having two to three hydroxy groups per molecule and having a number-average molecular weight of not less than 1800, the polyol 2 having two or more hydroxy groups per molecule and having a number-average molecular weight of not more than 200, and the urethanization reaction catalyst contains an organic tin catalyst, and an amine catalyst represented by Formula (1) or a blocked amine catalyst in which the amine catalyst is blocked with an acid, ##STR00011## where X represents an oxygen atom, or a nitrogen atom to which one alkyl group is bonded, R.sub.1 to R.sub.4 each independently represent an alkyl group, the alkyl group may have an ether bond, R.sub.1 and R.sub.2 may be bonded together to form a cyclic structure, and R.sub.3 and R.sub.4 may be bonded together to form a cyclic structure.

16. The urethane adhesive composition according to claim 15, wherein the main agent further contains a polyisocyanate B.

17. The urethane adhesive composition according to claim 16, wherein the polyisocyanate A and the polyisocyanate B each independently include at least one selected from the group consisting of diphenylmethane diisocyanate, polymeric MDI, and modified MDI.

18. The urethane adhesive composition according to claim 15, wherein the urethane prepolymer further contains unreacted polyisocyanate A in the polyisocyanate A.

19. The urethane adhesive composition according to claim 15, wherein in the organic tin catalyst, a ligand coordinated to a tin atom has a sulfur atom as a coordinating atom coordinated to the tin atom.

20. The urethane adhesive composition according to claim 15, wherein the polyol 1 includes at least a polyol having three hydroxy groups per molecule and having a number-average molecular weight of not less than 4800.

21. The urethane adhesive composition according to claim 15, wherein the polyoxyalkylene polyol has three hydroxy groups per molecule and has a number-average molecular weight of not less than 4,800.

22. The urethane adhesive composition according to claim 15, wherein the polyol 2 has two hydroxy groups per molecule.

23. The urethane adhesive composition according to claim 15, wherein the polyol 2 is 1,4-butanediol.

24. The urethane adhesive composition according to claim 15, wherein a content of the zeolite is not less than 3 mass % of a total amount of the curing agent.

25. The urethane adhesive composition according to claim 15, wherein a ratio of the number of isocyanate reactive groups in the curing agent to the number of all isocyanate groups in the main agent is 0.6 to 1.0.

26. The urethane adhesive composition according to claim 15, wherein a content of the urethanization reaction catalyst is 0.001 to 1.0 mass % of a total amount of the curing agent.

27. The urethane adhesive composition according to claim 15, wherein an elastic modulus after full curing is not less than 15 MPa.

28. The urethane adhesive composition according to claim 15, wherein the curing agent further contains a polyamine.

Description

EXAMPLES

[0239] The present technology is described below more specifically by way of examples. However, the present technology should not be construed as being limited to the following examples.

<Preparation of Urethane Prepolymer>

[0240] A polyol 1-1, a polyol 1-2, a polyisocyanate A-1, a polyisocyanate A-2, and a plasticizer shown in Table 1 below were used to have each composition (parts by mass) shown in the same table.

[0241] In preparation of urethane prepolymers with Formulations 1 to 4 shown in Table 1, the molar ratio of isocyanate groups that the polyisocyanate A-1 or the polyisocyanate A-2 had to the sum of hydroxy groups that the polyol 1-1 and the polyol 1-2 had (NCO groups/OH groups) was as follows. [0242] NCO groups/OH groups in preparation of a urethane prepolymer with Formulation 1: 2.0 [0243] NCO groups/OH groups in preparation of a urethane prepolymer with Formulation 2: 2.0 [0244] NCO groups/OH groups in preparation of a urethane prepolymer with Formulation 3: 13.3 [0245] NCO groups/OH groups in preparation of a urethane prepolymer with Formulation 4: 19.9

[0246] A mixture of the foregoing components was reacted under the condition of 80° C. for 5 hours to prepare each urethane prepolymer.

[0247] For the urethane prepolymers prepared as above, the urethane prepolymer with Formulation 1 may contain a urethane prepolymer having an isocyanate group and an unreacted polyisocyanate A-1. The same applies to the urethane prepolymer with Formulation 2.

[0248] On the other hand, the urethane prepolymer with Formulation 3 contains a urethane prepolymer having an isocyanate group and an unreacted polyisocyanate A-2. The same applies to the urethane prepolymer with Formulation 4.

«Manufacture of Composition»

<Main Agent>

[0249] With each of the urethane prepolymers prepared as above, the other components (polyisocyanate B, filler 1) shown in Table 1 were used to have the relevant composition (parts by mass) shown in the same table, and all the components were mixed with a stirrer to manufacture a main agent.

(Calculation of the Isocyanate Group Content Based on the Total Amount of the Main Agent)

[0250] The isocyanate group content based on the total amount of each main agent was calculated as described below. The results are shown in Table 1.

[0251] When the isocyanate component was the urethane prepolymer (urethane prepolymers prepared in Formulations 3 and 4 in Table 1), the isocyanate group content based on the total amount of the main agent was calculated by the NCO amount calculation method I described above.

[0252] For Formulation 3, the isocyanate group content percentage (mass %) of the isocyanate component (the mixture of the urethane prepolymer and the plasticizer) as measured with a potentiometric titrator by the A method according to JIS K-1603-1:2007 was 10.8 mass %.

[0253] For Formulation 4, the isocyanate group content percentage (mass %) of the isocyanate component (the mixture of the urethane prepolymer and the plasticizer) as measured with a potentiometric titrator by the A method according to JIS K-1603-1:2007 was 17.3 mass %.

[0254] When the isocyanate component comprises the urethane prepolymer and the polyisocyanate B (Formulations 1 and 2 in Table 1), the isocyanate group content based on the total amount of the main agent is calculated by the NCO amount calculation method II described above.

[0255] For Formulation 1, the isocyanate group content percentage (mass %) of the isocyanate component (the mixture of the urethane prepolymer, the polyisocyanate B, and the plasticizer) as measured with a potentiometric titrator by the A method according to JIS K-1603-1:2007 was 10.8 mass %.

[0256] For Formulation 2, the isocyanate group content percentage (mass %) of the isocyanate component (the mixture of the urethane prepolymer, the polyisocyanate B, and the plasticizer) as measured with a potentiometric titrator by the A method according to JIS K-1603-1:2007 was 10.8 mass %.

TABLE-US-00001 TABLE 1 Formulation 1st table (main agent) 1 2 3 4 Polyol 1-1 EXCENOL5030 100.0 50.0 100.0 100.0 Polyol 1-2 EXCENOL2020 0.0 50.0 0.0 0.0 Polyisocyanate A-1 MILLIONATE MT 14.7 19.8 0.0 0.0 Polyisocyanate A-2 CORONATE MX 0.0 0.0 112.4 168.8 Polyisocyanate B CORONATE MX 94.0 94.1 0.0 0.0 Plasticizer DINP 67.4 70.9 67.5 0.0 Filler 1 Niteron #300 69.0 71.1 70.0 67.2 Isocyanate group content based on total 8.7 8.7 8.7 13.8 amount of main agent (mass %)

[0257] Details of the components shown in Table 1 are as follows.

(Polyol 1)

[0258] Polyol 1-1: Polyoxypropylene triol having three hydroxy groups per molecule and having a number-average molecular weight of 5000; EXCENOL 5030 manufactured by AGC Inc. [0259] Polyol 1-2: Polyoxypropylene diol having two hydroxy groups per molecule and having a number-average molecular weight of 2000; EXCENOL 2020 manufactured by AGC Inc.

(Polyisocyanate A)

[0260] Polyisocyanate A-1: 4,4′-Diphenylmethane diisocyanate (pure MDI); MILLIONATE MT manufactured by Tosoh Corporation; molecular weight: 250. [0261] Polyisocyanate A-2: Carbodiimide modification of MDI; CORONATE MX manufactured by Tosoh Corporation; having two isocyanate groups per molecule (for CORONATE MX, hereinafter the same). [0262] Polyisocyanate B: Carbodiimide modification of MDI; CORONATE MX manufactured by Tosoh Corporation. [0263] Plasticizer: DINP (diisononyl phthalate) [0264] Filler 1: Carbon black; Niteron #300 manufactured by NIPPON STEEL Carbon Co., Ltd.

<Curing Agent>

[0265] The components shown in Table 2 below were used to have each composition (parts by mass) shown in the same table and mixed with a stirrer to manufacture a curing agent.

TABLE-US-00002 TABLE 2 Formulation 2nd table (curing agent) 1 2 3 4 5 Polyoxyalkylene polyol PREMINOL7001K 100.0 100.0 100.0 100.0 100.0 (high molecular weight) Polyol 2 1,4-Butanediol 10.3 10.3 10.3 10.3 10.3 (low molecular weight) Polyamine JEFFAMINE D-400 2.3 2.3 2.3 2.3 2.3 Filler 2 NANOX 30 89.6 Filler 3 ST-BCK 89.6 89.6 89.6 89.6 Zeolite Zeolum A-4 10.7 10.7 10.7 10.7 10.7 Organic tin catalyst 1 U-860 0.043 0.043 0.043 0.043 Organic tin catalyst 2 U-810 0.043 Comparative amine catalyst 1 DABCO 33LV Specific amine catalyst 1 DMDEE 0.427 0.427 0.427 Specific amine catalyst 2 TOYOCAT ET 0.427 Specific amine catalyst 3 TOYOCAT ETF 0.427 Specific amine catalyst 4 TOYOCAT ET + cyanoacetic acid Comparative amine catalyst 2 U-CAT SA-1 Comparative amine catalyst 3 TOYOCAT RX5 Amount (parts by mass) of zeolite with respect 248.8 248.8 248.8 248.8 248.8 to 1 part by mass of organic tin catalyst 1 Formulation 2nd table (curing agent) (continuation) 6 7 8 9 10 Polyoxyalkylene polyol PREMINOL7001K 100.0 100.0 100.0 100.0 100.0 (high molecular weight) Polyol 2 1,4-Butanediol 10.3 10.2 10.3 10.3 19.3 (low molecular weight) Polyamine JEFFAMINE D-400 2.3 2.2 Filler 2 NANOX 30 Filler 3 ST-BCK 87.5 89.2 89.6 97.9 88.7 Zeolite Zeolum A-4 10.4 10.5 10.7 11.1 Organic tin catalyst 1 U-860 0.042 0.043 0.042 0.011 Organic tin catalyst 2 U-810 Comparative amine catalyst 1 DABCO 33LV 0.314 Specific amine catalyst 1 DMDEE 0.209 Specific amine catalyst 2 TOYOCAT ET 0.444 Specific amine catalyst 3 TOYOCAT ETF Specific amine catalyst 4 TOYOCAT ET + cyanoacetic acid Comparative amine catalyst 2 U-CAT SA-1 0.427 Comparative amine catalyst 3 TOYOCAT RX5 Amount (parts by mass) of zeolite with respect 247.6 — 248.8 — 1009.1 to 1 part by mass of organic tin catalyst 1 Formulation 2nd table (curing agent) (continuation) 11 12 13 14 15 Polyoxyalkylene polyol PREMINOL7001K 100.0 100.0 100.0 100.0 100.0 (high molecular weight) Polyol 2 1,4-Butanediol 20.5 10.3 10.3 10.3 10.3 (low molecular weight) Polyamine JEFFAMINE D-400 2.3 2.3 2.3 2.3 Filler 2 NANOX 30 Filler 3 ST-BCK 96.2 89.6 89.6 89.6 89.6 Zeolite Zeolum A-4 11.5 10.7 10.7 6.4 21.4 Organic tin catalyst 1 U-860 0.043 0.043 0.043 0.043 Organic tin catalyst 2 U-810 Comparative amine catalyst 1 DABCO 33LV 0.481 Specific amine catalyst 1 DMDEE 0.458 Specific amine catalyst 2 TOYOCAT ET 0.427 0.427 Specific amine catalyst 3 TOYOCAT ETF Specific amine catalyst 4 TOYOCAT ET + 0.427 cyanoacetic acid Comparative amine catalyst 2 U-CAT SA-1 Comparative amine catalyst 3 TOYOCAT RX5 0.427 Amount (parts by mass) of zeolite with respect — 248.8 248.8 149.3 497.7 to 1 part by mass of organic tin catalyst 1

[0266] Details of the components shown in Table 2 are as follows.

(Polyoxyalkylene Polyol)

[0267] Polyoxyalkylene polyol (high molecular weight):

[0268] Polyoxyalkylene triol having three hydroxy groups per molecule, having a number-average molecular weight of 6000, and having an end to which ethylene oxide is added; PREMINOL 7001K manufactured by AGC Inc.

(Polyol 2)

[0269] Polyol 2 (low molecular weight): 1,4-Butanediol; manufactured by Mitsubishi Chemical Corporation. [0270] Polyamine: Polyoxypropylene-α,ω-diamine; JEFFAMINE D-400 manufactured by Huntsman. [0271] Filler 2: Calcium carbonate; NANOX 30 manufactured by Maruo Calcium Co., Ltd. [0272] Filler 3: Clay; ST-BCK manufactured by Agrochemitech; calcined clay. [0273] Zeolite: A-type zeolite; “Zeolum A-4” manufactured by Tosoh Corporation; molar ratio of SiO.sub.2/Al.sub.2O.sub.3=2 to 2.5; powder; size: 0.15 mm or less (with 100 mesh).

(Organic Tin Catalyst)

[0274] Organic tin catalyst 1: Dioctyltin bis(octyl thioglycollate) (with the structure below); NEOSTANN U-860 manufactured by Nitto Kasei Co., Ltd.

##STR00005## [0275] Organic tin catalyst 2: Dioctyltin dilaurate; NEOSTANN U-810 manufactured by Nitto Kasei Co., Ltd. [0276] Comparative amine catalyst 1: 1,4-Diazabicyclo[2.2.2]octane (with the structure below); DABCO 33LV manufactured by Air Products Inc.

##STR00006##

(Specific Amine Catalyst)

[0277] Specific amine catalyst 1: DMDEE; dimorpholinodiethyl ether (manufactured by San-Apro Ltd.); with the structure below.

##STR00007## [0278] Specific amine catalyst 2: Bis(N,N-dimethyl-2-aminoethyl)ether (with the structure below); TOYOCAT ET manufactured by Tosoh Corporation.

##STR00008## [0279] Specific amine catalyst 3: A blocked amine catalyst in which TOYOCAT ET is blocked with an acid; TOYOCAT ETF manufactured by Tosoh Corporation. In the specific amine catalyst 3, the acid used for blocking is a formic acid. [0280] Specific amine catalyst 4: A blocked amine catalyst in which TOYOCAT ET is blocked with a cyanoacetic acid serving as the acid in a molar ratio of TOYOCAT ET:acid of 1:2; manufactured by mixing TOYOCAT ET and a cyanoacetic acid in a molar ratio of TOYOCAT ET:cyanoacetic acid of 1:2 while cooling them in a water bath at 10° C. [0281] Comparative amine catalyst 2: A catalyst in which diazabicycloundecene is blocked with a phenol (with the structure below); NEOSTANN U-CAT SA-1 manufactured by Nitto Kasei Co., Ltd.

##STR00009## [0282] Comparative amine catalyst 3: N,N,N′-Trimethylaminoethylethanolamine (with the structure below); TOYOCAT RX5 manufactured by Tosoh Corporation.

##STR00010##

<Two-Part Urethane Adhesive Composition>

[0283] The main agents and the curing agents prepared as above were combined in combinations of the formulation numbers as shown in the third table to prepare two-part urethane adhesive compositions.

[0284] For each of the urethane adhesive compositions, the agents were stirred and mixed under the conditions of 23° C. and 50% RH. The ratio of the number of isocyanate reactive groups in the curing agent to the number of isocyanate groups in the main agent (isocyanate reactive groups/isocyanate groups) in this process is shown in the third table.

TABLE-US-00003 TABLE 3 Example 3rd table (urethane adhesive composition) A B C D E F Main agent (formulation No.) 1 2 3 1 1 1 Curing agent (formulation No.) 1 1 1 2 3 4 Ratio of number of isocyanate 0.8 0.8 0.8 0.8 0.8 0.8 reactive groups in curing agent to number of isocyanate groups in main agent (isocyanate reactive groups/isocyanate groups) Presence or absence of foaming Excellent Excellent Excellent Excellent Good Excellent (evaluation criteria for foaming minimizing performance) Evaluation of Shear strength Good Good Good Excellent Excellent Good adhesion development rate development after one day performance Shear failure mode Good Good Good Good Good Good after one day Elastic modulus after full curing (MPa) 35 35 35 35 35 30 Example 3rd table (urethane adhesive composition) G H I J K Main agent (formulation No.) 1 4 1 2 2 Curing agent (formulation No.) 5 10 13 14 15 Ratio of number of isocyanate 0.8 0.8 0.8 0.8 0.8 reactive groups in curing agent to number of isocyanate groups in main agent (isocyanate reactive groups/isocyanate groups) Presence or absence of foaming Excellent Excellent Excellent Good Excellent (evaluation criteria for foaming minimizing performance) Evaluation of Shear strength Good Good Excellent Excellent Good adhesion development rate development after one day performance Shear failure mode Fair Good Good Good Fair after one day Elastic modulus after full curing (MPa) 35 200 35 35 40 Comparative Example 3rd table (urethane adhesive composition) (continuation) a b c d e f Main agent (formulation No.) 1 1 1 1 4 1 Curing agent (formulation No.) 6 7 8 9 11 12 Ratio of number of isocyanate 0.8 0.8 0.8 0.8 0.8 0.8 reactive groups in curing agent to number of isocyanate groups in main agent (isocyanate reactive groups/isocyanate groups) Presence or absence of foaming Excellent Excellent Excellent Poor Excellent Excellent (evaluation criteria for foaming minimizing performance) Evaluation of Shear strength Poor Poor Poor Poor Poor Poor adhesion development rate development after one day performance Shear failure mode Good Poor Good Poor Poor Good after one day Elastic modulus after full curing (MPa) 35 35 35 28 200 35

<Evaluation>

[0285] The urethane adhesive compositions thus mixed were evaluated as described below. The results thereof are shown in the third table.

(Production of Specimen)

[0286] Two adherends (width: 25 mm; length: 70 mm; thickness: 1.6 mm) formed from an electrodeposition coated sheet (the trade name of an electrodeposition coating paint: GT-10LF; manufactured by Kansai Paint Co., Ltd.) were prepared.

[0287] Next, each of the urethane adhesive compositions that had just prepared (mixed) was applied onto a surface of one of the two adherends to be 25 mm wide (to conform the width of the adherend) and 10 mm long (in the longitudinal direction of the adherend), whereafter the one adherend and the other adherend were adhered and press-bonded together to have a thickness of the applied urethane adhesive composition of 2 mm. Thus a specimen was prepared.

(Curing Condition)

Curing Condition 1

[0288] Each of the specimens produced as above was placed under the conditions of 23° C. and 50% RH for 24 hours to cure the relevant urethane adhesive composition.

Curing Condition 2 (Full Curing)

[0289] Each of the specimens produced as above was placed under the conditions of 23° C. and 50% RH for 7 days to cure the relevant urethane adhesive composition.

[0290] In the present technology, the curing conditions for full curing are defined as Curing condition 2 as above.

(Shear Test)

[0291] Each of the specimens produced as above was subjected to a tensile test (pulling rate: 50 mm/min) according to JIS K 6850:1999 under the condition of 23° C. to measure the shear adhesion strength, and the presence or absence of foaming in each of the specimens as well as the failure mode after the shear test were visually checked.

(Presence or Absence of Foaming: Evaluation Criteria for Foaming Minimizing Performance)

[0292] Each of cured products of the specimens produced as above was cut, and the cut surface of the cured product was visually observed and also magnified with a 50× magnifying glass and then observed.

[0293] When there was no foaming in the cut surface of the cured product in observation of the cut surface magnified with the magnifying glass, the foaming minimizing performance was rated as very excellent and denoted as “Excellent.”

[0294] When foaming was seen in the cut surface of the cured product in observation of the cut surface magnified with the magnifying glass, the foaming minimizing performance was rated as fairly good and denoted as “Good.”

[0295] When foaming was seen in the cut surface in visual observation without the need for magnification through the magnifying glass, the foaming minimizing performance was rated as poor and denoted as “Poor.”

(Evaluation of Adhesion Development Performance)

[0296] In the present technology, the adhesion development performance was evaluated based on results of the shear strength development rate after one day (shear strength development rate) and the shear failure mode after one day, which are described below.

Shear Strength Development Rate After One Day (Shear Strength Development Rate)

[0297] Using the same type of the urethane adhesive composition, when the shear strength development rate after one day (the percentage of the shear adhesion strength of a specimen having been subjected to Curing condition 1 with respect to the shear adhesion strength of a specimen having been subjected to Curing condition 2) was 80% or more, this was denoted as “Excellent.”

[0298] When the shear strength development rate after one day was 65% or more and less than 80%, this was denoted as “Good.”

[0299] When the shear strength development rate after one day was less than 65%, this was denoted as “Poor.”

Shear Failure Mode After One Day (CF Rate)

[0300] For the failure mode after the shear test of a specimen having been subjected to Curing condition 1, when the CF rate (the percentage of an area having cohesive failure (CF) with respect to the entire area of the adhesion surface) was 100%, this was denoted as “Good.”

[0301] When the CF rate was 60% or more and less than 100%, this was denoted as “Fair.”

[0302] When the CF rate was less than 60%, this was denoted as “Poor.”

(Evaluation Criteria for Adhesion Development Performance)

[0303] In the present technology, when the shear strength development rate after one day (shear strength development rate) was 65% or more and the shear failure mode after one day (CF rate) was 60% or more, the adhesion development performance was rated as excellent.

[0304] In the foregoing case, the adhesion development performance was evaluated to be more excellent as the shear strength development rate was higher or the CF rate was higher. When evaluation results of the CF rate were the same for instance, a specimen with a higher shear strength development rate was evaluated to have more excellent adhesion development performance.

[0305] When the shear strength development rate was less than 65% or when the CR rate was less than 60%, the adhesion development performance was evaluated to be poor.

Elastic Modulus After Full Curing

[0306] Each of the specimens having been subjected to Curing condition 2 was subjected to a tensile test (pulling rate: 200 mm/min) according to JIS K 6850:1999 under the condition of 23° C. to measure a tensile elastic modulus (unit: MPa). The results thereof are shown in the “Elastic modulus after full curing” space in Table 3.

[0307] As the elastic modulus after full curing is higher, the adhesion strength after full curing is higher and thus favorable.

[0308] As evident from the results shown in Table 3, in Comparative Example a where no specific amine catalyst was used, the adhesion development performance (particularly the shear strength development rate) was poor.

[0309] In Comparative Example b where no organic tin catalyst was used and instead the comparative amine catalyst 1 was used, the adhesion development performance was poor.

[0310] In Comparative Example c where no specific amine catalyst was used and instead the comparative amine catalyst 2 was used, the adhesion development performance (particularly the shear strength development rate) was poor.

[0311] In Comparative Example d where neither zeolite nor specific amine catalyst was used, the foaming minimizing performance and the adhesion development performance were poor.

[0312] In Comparative Example e where no organic tin catalyst was used, the adhesion development performance was poor.

[0313] In Comparative Example f where no specific amine catalyst was used and instead the comparative amine catalyst 3 was used, the adhesion development performance (particularly the shear strength development rate) was poor.

[0314] In contrast, in each of the urethane adhesive compositions according to the technology, the main agent had a high isocyanate group content, and excellent adhesion strength was allowed to develop even when a dehydrating agent was used, while foaming in the cured product was able to be minimized.