JP6766440B2 - Adhesive composition - Google Patents

Description

The present invention relates to curable resin compositions that are suitably used for adhesives.

The curable resin composition used for the adhesive includes a one-component type that is cured by moisture in the air, a two-component type that is cured by mixing a curing agent such as a polyol or a polyamine, and a latent curing agent 1. .5 Liquid type and the like, and examples of the main component for forming such a polyurethane composition include a curable resin composition containing an NCO group-terminated urethane prepolymer obtained by reacting isocyanate and a polyol, a filler, and an additive. Those are widely used, and as the polyol, for example, polytetramethylene glycol, polyester polyol, polyalkylene oxide and the like are used.

A curable resin composition using a polyester polyol has a high viscosity and tends to be inferior in handleability, and a polyurethane composition obtained by using the polyester polyol contains an ester group, so that the water resistance is inferior due to hydrolysis. There is a problem that the transition temperature (Tg) is high and the cold resistance is inferior.

On the other hand, the polyurethane composition using polytetramethylene glycol is excellent in hydrolysis resistance and cold resistance, and therefore can be suitably used in applications requiring such properties. However, polytetramethylene glycol is usually a solid in a room temperature environment, and when used, it is usually used by heating or dissolved in other components, and has a short pot life and is curable. The resin composition has a problem that it tends to be inferior in workability. Further, the polyurethane obtained by using it tends to have poor flexibility due to its crystallinity, and there is a problem that its use is limited.

Further, these polyols are generally limited to a molecular weight of about 4000, and it is difficult to increase the molecular weight, and there is a limit to imparting flexibility to the polyurethane composition obtained by using the same.
Polyalkylene oxides produced by addition polymerization of alkylene oxides such as propylene oxide are generally liquid and have a low viscosity, and curable resin compositions using such polyalkylene oxides are excellent in handleability and moldability.

Polyalkylene oxides are industrially produced by addition polymerization of alkylene oxides such as propylene oxide and ethylene oxide using an alkali metal such as potassium hydroxide as a catalyst.

However, when the polyalkylene oxide is produced by this method, the obtained polyalkylene oxide produces a large amount of monool and has a high degree of unsaturation. Therefore, a curable resin composition using such a polyalkylene oxide is used. Has a problem of poor curability, and may require a long curing period due to the time required for curing, or may require an increase in the amount of catalyst, resulting in poor storage stability of the composition. Further, there is a problem that it is difficult to obtain a uniform cured product by foaming due to moisture in the air and the workability is poor.

Further, the polyurethane composition using such a polyalkylene oxide having a high degree of unsaturation does not easily extend its molecular weight due to monool and contains a large amount of low molecular weight components, so that it easily bleeds from the urethane composition over time and contaminates the surroundings. Improvement was sought.

As a polyurethane using a polyalkylene oxide having a reduced degree of unsaturation, for example, a polyurethane obtained by reacting a polyalkylene oxide obtained by using cesium hydroxide or the like as a catalyst with a polyisocyanate compound has been proposed ( For example, see Patent Document 1). However, the degree of unsaturation of the polyalkylene oxide described in Patent Document 1 is still high, and the obtained polyurethane still does not exhibit sufficient curability and low contamination.

Further, a polyurethane obtained by reacting a polyalkylene oxide obtained by using a specific phosphazenium salt as a catalyst with a polyisocyanate compound has been proposed (see, for example, Patent Document 2). However, the degree of unsaturation of the polyalkylene oxide described in Patent Document 2 is still high, and it cannot be said that sufficient curability and low contamination are still exhibited.

As a polyalkylene oxide having a further reduced degree of unsaturation, a polyalkylene oxide obtained by using a compound metal cyanide complex as a catalyst is known (see, for example, Patent Document 3). However, the polyalkylene oxide described in Patent Document 3 has a problem such as poor handleability because it has a wide molecular weight distribution of about 1.1 and a high viscosity, and a curable resin composition using the polyalkylene oxide has a viscosity. There is a problem that it rises and is inferior in workability when it is applied as an adhesive, and there is a problem that gas generated by a reaction with moisture in the air is poorly released and easily foams.

Furthermore, since the polyurethane composition obtained by using the polyurethane composition tends to be non-uniform, the improvement of the contamination property by bleeding from the adhesive is not sufficient, and further improvement is required.

Japanese Patent Application Laid-Open No. 8-176263 JP-A-11-124424 Japanese Patent Application Laid-Open No. 4-59825

The present invention has been made in view of the above background techniques, and an object of the present invention is to provide an adhesive composition having excellent workability, foaming resistance, and curability, and a cured product having low contamination. ..

As a result of diligent studies to solve the above problems, the present inventors have made an NCO group composed of a polyalkylene oxide unit and a polyisocyanate unit having a specific molecular weight distribution with a specific degree of unsaturation in a specific composition ratio. We have found that a composition containing a terminal urethane prepolymer can solve the above problems, and have completed the present invention.

That is, the present invention relates to the following adhesive compositions.

[1] One selected from the group consisting of an NCO group-terminated urethane prepolymer which is a reaction product of an active hydrogen-containing compound (A) and a polyisocyanate (B), a filler (C) and an additive (D). Alternatively, it is a curable resin composition containing two or more kinds.
The active hydrogen-containing compound (A) contains one or more polyalkylene oxides selected from the group consisting of bifunctional polyalkylene oxides (A1) and trifunctional or higher functional polyalkylene oxides (A2).
The more component of the bifunctional polyalkylene oxide (A1) and the trifunctional or higher functional polyalkylene oxide (A2) satisfies all of the following (a) to (d), and the NCO group-terminated urethane prepolymer is as follows. An adhesive composition characterized by satisfying (e).
(A) The degree of unsaturation is 0.010 meq / g or less.
(B) The number average molecular weight calculated from the hydroxyl value (OHV) is 1000 or more.
(C) The molecular weight distribution (Mw / Mn) determined by the (GPC) method by gel permeation chromatography using polystyrene as a standard substance is 1.039 or less.
(D) The molecular weight distribution (Mw / Mn) obtained by the gel permeation chromatography (GPC) method and the number average molecular weight (M) calculated from the hydroxyl value (OHV) satisfy the following mathematical formula (1).

(E) The ratio (NCO / OH) of the total amount of NCO groups contained in the polyisocyanate (B) to the total amount of OH groups contained in the active hydrogen-containing compound (A) is 1.71 to 3.00 (molar ratio).

[2] The polyisocyanate (C) is polymethylene polyphenylene polyisocyanate (polymeric MDI), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane. Diisocyanate, 1,5-naphthalenediocyanate, trizine diisocyanate, xylylene diisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, pentamethylene diisocyanate, 1,6-hexamethylene The composition according to the above [1], which is at least one selected from the group consisting of diisocyanates, these isocyanate-containing prepolymers, and modified products of these isocyanates.

[3] above [1 average functionality _{f ave} polyalkylene oxide (A1) and polyalkylene oxide (A2) and the combined polyalkylene oxide mixture, characterized in that in the range of 2.01 to 3.00 ] Or the composition according to [2].

[4] The composition according to any one of the above [1] to [3], wherein the filler (C) contains one or more inorganic fillers.

[5] The additive (D) is characterized by containing one or more selected from the group consisting of a urethanization catalyst, a light stabilizer, an antioxidant, a plasticizer, and a solvent. The composition according to any one of [4].

[6] The molecular weight distribution (Mw / Mn) of polyalkylene oxide obtained by gel permeation chromatography (GPC) using polystyrene as a standard substance is as follows: 4 columns in which a separation column is filled with a filler having a particle size of 3 μm. The composition according to any one of the above [1] to [5], which has a molecular weight distribution analyzed under the conditions of connecting in series, connecting a resistance tube to the reference side, and using tetrahydrofuran as a developing solvent.

The adhesive composition of the present invention has a low viscosity even when a polyalkylene oxide having a low degree of unsaturation is used, and is excellent in workability, foaming resistance, and curability.

In addition, the adhesive composition of the present invention has less bleeding after curing, has low contamination, and can be suitably used as an adhesive.

The present invention will be described in detail below.

The adhesive composition of the present invention comprises an NCO group-terminated urethane prepolymer which is a reaction product of an active hydrogen-containing compound (A) and a polyisocyanate (B), a filler (C) and an additive (D). A curable resin composition containing one or more selected from the group.
The active hydrogen-containing compound (A) contains one or more polyalkylene oxides selected from the group consisting of bifunctional polyalkylene oxides (A1) and trifunctional or higher functional polyalkylene oxides (A2).
The more component of the bifunctional polyalkylene oxide (A1) and the trifunctional or higher functional polyalkylene oxide (A2) satisfies all of the following (a) to (d), and the NCO group-terminated urethane prepolymer is as follows. Its characteristic is to satisfy (e).
(A) The degree of unsaturation is 0.010 meq / g or less.
(B) The number average molecular weight calculated from the hydroxyl value (OHV) is 1000 or more.
(C) The molecular weight distribution (Mw / Mn) determined by the (GPC) method by gel permeation chromatography using polystyrene as a standard substance is 1.039 or less.
(D) The molecular weight distribution (Mw / Mn) obtained by the gel permeation chromatography (GPC) method and the number average molecular weight (M) calculated from the hydroxyl value (OHV) satisfy the above formula (1).
(E) The ratio (NCO / OH) of the total amount of NCO groups contained in the polyisocyanate (B) to the total amount of OH groups contained in the active hydrogen-containing compound (A) is 1.71 to 3.00 (molar ratio).

<Chemical composition of polyalkylene oxide>
In the present invention, the bifunctional polyalkylene oxide (A1) is not particularly limited, but for example, one or more active hydrogen-containing compounds R [-H] m are used, and the number of carbon atoms is 2 to 12. It is preferable that it is an alkylene oxide adduct to which one or more kinds of 3-membered ring alkylene oxides are added, and it is preferable that it is a polyalkylene oxide represented by the following general formula (1).

[In the above general formula (1), R is an m-valent group obtained by removing m active hydrogens from the active hydrogen-containing compound (R [−H] _m ), and Z is an alkylene group having 2 to 12 carbon atoms. Alternatively, it is a cycloalkylene group, and A is an alkylene group having 3 carbon atoms. When there are a plurality of Z or A, each may be the same or different. m is 2, p is an integer of 0 or 1 to 500, q is an integer of 1 to 1000, and r is an integer of 0 or 1 to 500. ]
Further, in the present invention, the trifunctional polyalkylene oxide (A2) is not particularly limited, but for example, one or more active hydrogen-containing compounds R [-H] m are used, and the number of carbon atoms is 2. It is preferably an alkylene oxide adduct to which one or more of the three-membered ring alkylene oxides of ~ 12 are added, and in the above general formula (1), R is an active hydrogen-containing compound (R [−H]. It is an m-valent group obtained by removing m active hydrogens from m), Z is an alkylene group having 2 to 12 carbon atoms or a cycloalkylene group, and A is an alkylene group having 3 carbon atoms (plural Z or If there is A, they may be the same or different), m is an integer of 3 to 100, p is an integer of 0 or 1 to 500, q is an integer of 1 to 1000, and r is an integer of 0 or 1 to 500. It is preferably an integer polyalkylene oxide.

Among these, a compound having an oxyalkylene group and having at least one active hydrogen group per molecule in a molecule at an arbitrary position such as a polymer terminal or a branched chain terminal is preferable.

The active hydrogen-containing compound (R [−H] _m ) is not particularly limited as long as it has an active hydrogen group, and is, for example, water, propylene glycol, ethylene glycol, diethylene glycol, dipropylene glycol, butylene glycol, 1, Bifunctional diols such as 6-hexanediol, tripropylene glycol, triethylene glycol and polyoxyalkylene diol, bisphenols such as bisphenol A, bisphenol F and bisphenol AD, dihydroxybenzenes such as catechol, resorcin and hydroquinone, methyl Examples thereof include compounds having two active hydrogen groups such as amines such as amines, ethylamines, propylamines and butylamines. As the active hydrogen-containing compound (R [−H] _m ), one or a mixture of two or more selected from these can be used.

The alkylene oxide to be added to the active hydrogen-containing compound (R [−H] _m ) may be a compound having one or more epoxy rings in the molecule, and is not particularly limited, but for example, ethylene oxide or propylene oxide. , Butylene oxide, styrene oxide and other alkylene oxides having 2 to 12 carbon atoms, and one or more kinds of alkylene oxides may be used.

Among these, one or more alkylene oxides containing alkylene oxides having 2 to 3 carbon atoms such as propylene oxide and ethylene oxide, which are easily available industrially, are preferable, and one or more alkylene oxides containing propylene oxide are preferable. Ethylene oxide is more preferred.

Since the ZO in the general formula (1) tends to have a low viscosity and easily exhibits good urethane moldability, it is a poly derived from an alkylene oxide having 2 to 12 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide, and styrene oxide. It preferably has an ether structure. More preferably, it is a one-type or two or more kinds of alkylene oxide-derived polyether structure selected from ethylene oxide and propylene oxide, and most preferably a kind of polyether structure selected from ethylene oxide and propylene oxide.

In the general formula (1), p is an integer of 0 or 1 to 500, preferably an integer of p = 0 or 1 to 100, and more preferably p = 0.

Examples of Z in the general formula (1) include a structure represented by the following general formula (2).

[In the above general formula (2), R ₂ , R ₃ , R ₄ , and R ₅ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and a cycloalkyl having 3 to 10 carbon atoms. However, the total number of carbon atoms of R _{2 to} R ₅ does not exceed 10. It is also possible to form any two members to cycloalkyl group R ₂ to R _5. ]
Further, the AO in the general formula (1) has a polyether structure derived from an alkylene oxide having 3 carbon atoms such as propylene oxide because the viscosity tends to be low and good mechanical properties are easily exhibited when polyurethane is used. Is preferable.

Examples of A in the general formula (1) include a structure represented by the following formula.

Q in the general formula (1) is an integer of 1 to 1000, preferably an integer of q = 10 to 500, and more preferably an integer of q = 15 to 250.

R in the general formula (1) is an integer of 0 or 1 to 500. Since it is difficult to solidify at a low temperature and is easy to handle, it is preferably r = 0 or an integer of 1 to 90, and more preferably r = 0.

Regarding the relationship between p, q and r in the above general formula (1), since the viscosity tends to be low and good mechanical properties are likely to be exhibited when polyurethane is used, p + q> r (however, p + q is 10 to 1000, q). Is preferably 10 to 1000 and r is 0 or 1 to 90). More preferably, it satisfies p + q> 5r (where p + q is 30 to 600, q is 30 to 500, r is 0 or 1 to 90), and most preferably p + q> 10r (where p + q is 50 to 600, q). Is 50 to 500, and r is 0 or 1 to 90).

As the polyalkylene oxide (A1), m in the above general formula (1) is 2. The polyalkylene oxide (A2) is not particularly limited as long as m in the general formula (1) is in the range of 3 to 100, but is preferably in the range of 3 to 5.

When the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A), the molecular weight distribution tends to be narrow and the handleability is easily excellent. Therefore, the polyalkylene oxide (A) is preferable. ) Is a combination of m = 2 diol and polyalkylene oxide (B) is a combination of m = 3 triol.

When the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A), each of the polyalkylene oxide (A1) and the polyalkylene oxide (A2) has the above-mentioned structure. However, if the molecular structure of the polyalkylene oxide having the higher content has the above-mentioned structure, it can be preferably used.

<Molecular weight distribution of polyalkylene oxide>
When bifunctional polyalkylene oxide (A1) is used alone as the active hydrogen-containing compound (A), its molecular weight distribution (Mw / Mn) determined by gel permeation chromatography (GPC) using polystyrene as a standard substance. ) Is 1.039 or less. It is preferably in the range of 1.003 to 1.029, more preferably in the range of 1.005 to 1.019, and most preferably in the range of 1.006 to 1.016.

When trifunctional polyalkylene oxide (A2) is used alone as the active hydrogen-containing compound (A), its molecular weight distribution (Mw / Mn) determined by gel permeation chromatography (GPC) using polystyrene as a standard substance. ) Is not particularly limited, but is preferably 1.069 or less. It is more preferably in the range of 1.003 to 1.039, and even more preferably in the range of 1.005 to 1.019.

Furthermore, when a bifunctional polyalkylene oxide (A1) and a trifunctional or higher functional polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A), gel permeation chromatography (GPC) using polystyrene as a standard substance. The molecular weight distribution (Mw / Mn) of each of the polyalkylene oxide (A1) and the polyalkylene oxide (A2) determined by the method) is more preferably within the above range, but the polyalkylene oxide having the larger content If the molecular weight distribution (Mw / Mn) is within the above range, it can be preferably used.

When this molecular weight distribution (Mw / Mn) exceeds 1.039, in addition to the increase in viscosity, which is considered to be due to the increase in high molecular weight components and the decrease in monool, the deterioration of curability, which is considered to be due to the influence of low molecular weight components, is caused. It is easy to cause, and when a curable resin composition using it is used for adhesive use, it is difficult for bubbles to escape, resulting in poor workability and poor productivity, and bubbles generated during curing are also viscous and cannot be removed. It tends to be inferior in foam resistance.

In particular, when the molecular weight distribution (Mw / Mn) of the polyalkylene oxide (A1) exceeds 1.039, or when the degree of unsaturation described later exceeds 0.029 meq / g, the handleability in bulk is poor. Furthermore, the miscibility of the additives also deteriorates, and when the reaction or composition becomes non-uniform or the reaction becomes non-uniform, the cured product of such a curable resin composition contaminates the surroundings due to low molecular weight components and the like. Since it is easily caused, the polyalkylene oxide (A1) is preferably in the range of less than 20 parts by weight, more preferably less than 10 parts by weight, with respect to 100 parts by weight of the polyalkylene oxide (A2).

When the molecular weight distribution (Mw / Mn) of the polyalkylene oxides (A1) and (A2) is 1.029 or less, a remarkable viscosity reducing effect is obtained, the bulk handling property is improved, and the additives are mixed. The properties are also good, and the reaction and composition tend to be uniform.

When bifunctional polyalkylene oxide (A1) or trifunctional or higher functional polyalkylene oxide (A2) is used alone as the active hydrogen-containing compound (A), gel permeation chromatography (GPC) using polystyrene as a standard substance. The relationship between the molecular weight distribution (Mw / Mn) obtained by the method and the number average molecular weight (M) calculated from the polystyrene value (OHV) described later satisfies the above formula (1).

It is preferable to satisfy the following mathematical formula (2).

More preferably, the following mathematical formula (3) is satisfied.

When a bifunctional polyalkylene oxide (A1) and a trifunctional or higher functional polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A), the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are used. It is preferable that each of them satisfies the above formula, but if the polyalkylene oxide having a higher content satisfies the above formula, it can be preferably used.

The molecular weight distribution (Mw / Mn) determined by the gel permeation chromatography (GPC) method using polystyrene as a standard substance is obtained by connecting four columns in which a separation column is filled with a filler having a particle size of 3 μm in series for the reason described later. However, it is preferable that the molecular weight distribution is measured and analyzed under the condition that a resistance tube is connected to the reference side and tetrahydrofuran is used as the developing solvent, and the molecular weight distribution calculated by using a cubic approximate curve calibration curve using standard polystyrene. It is desirable that it is (Mw / Mn).

The number of separation columns is preferably 3 to 5 because the separation ability (theoretical plate number) is high and it is easy to suppress the spread of the molecular weight distribution due to fluctuations in the baseline and minute peaks of impurities in the liquid, which is particularly preferable. There are four.

The particle size of the packing material of the separation column is preferably 1 to 4.5 μm because the measurement time is appropriate and it is easy to suppress the expansion of the molecular weight distribution due to fluctuations in the baseline and minute peaks of impurities in the liquid. Particularly preferably, it is 3 μm.

The exclusion limit of the separation column is preferably 50,000 to 3 million, more preferably 60,000 to 400,000. The inner diameter of the separation column is preferably 5 to 7.5 mmφ, more preferably 6 mmφ. The length of the separation column is preferably 10 to 25 cm, more preferably 15 cm.

Examples of such a separation column include Tskgel Super H4000 and Tskgel Super H3000 manufactured by Tosoh Corporation. The most preferable configuration of the separation column is a configuration in which a total of four Tskgel SuperH4000 × 2 and Tskgel SuperH3000 × 2 manufactured by Tosoh are connected in series.

The flow velocity on the separation column side is preferably 0.5 to 0.9 ml / min, and more preferably 0.6 ml / min. The column temperature is preferably 30 ° C. to 50 ° C., more preferably 40 ° C.

Further, since it is easy to suppress the spread of the molecular weight distribution due to the pulsation of the pump on the reference side, it is preferable to connect 2 to 6 resistance tubes, more preferably 5 resistance tubes, and most preferably. It is a connection of 5 resistance tubes and 1 separation column.

As the resistance tube, a tube having a length of 2 m and an inner diameter of 0.1 mmφ is preferable.

The flow velocity on the reference side is preferably 0.1 to 0 in the state of 5 resistance tubes because the pulsation cycle of the pump is short and it is easy to suppress the fluctuation of the baseline and it is easy to suppress the expansion of the molecular weight distribution due to the pulsation of the pump. It is 6 ml / min, more preferably 0.15 ml / min.

The polystyrene used as the standard substance for the cubic approximate curve calibration curve is preferably 6 to 10 points, and more preferably 8 points. The molecular weight of polystyrene used in a standard substance having a known molecular weight is preferably selected from the range of 300 to 3000000, and more preferably selected from the range of 450 to 1100000. Specifically, for example, selection of 8 points of 500, 1010, 2630, 10200, 37900, 96400, 427000, 1090000 and the like can be mentioned, and measurement of the standard substance includes 4 points of 500, 2630, 37900, 427000 and 1010, 10200. It may be measured in two steps such as 4 points of 96400 and 1090000.

The developing solvent is preferably dimethylformamide or tetrahydrofuran, and more preferably BHT stabilizer-containing special grade tetrahydrofuran manufactured by Wako Pure Chemical Industries, Ltd.

The sample concentration is preferably 0.5 to 2 mg / ml, more preferably 1 mg / ml. The injection amount of the sample solution is preferably 10 to 90 μl, in which the peak is less likely to be broad and the molecular weight distribution is less likely to spread, and more preferably 20 μl.

The area ratio of the low molecular weight component in the gel permeation chromatography (GPC) method is preferably 4.5% or less of the entire peak, and more preferably 2% or less. The viscosity tends to increase as the area ratio of the low molecular weight component decreases, but it is preferable to use a polyurethane elastomer because it has few transition components and is easily excellent in handleability and mechanical properties.

In the present invention, the area ratio of the low molecular weight components of the polyalkylene oxides (A1) and (A2) in the gel permeation chromatography (GPC) method is preferably 4.5% or less of the total peak, and is 2%. The following is more preferable. The viscosity tends to increase as the area ratio of the low molecular weight component decreases, but it is preferable to use polyurethane because it has few transition components and is easily excellent in handleability and mechanical properties.

Here, the "area ratio of low molecular weight components" in the gel permeation chromatography (GPC) method is calculated when measuring the molecular weight distribution by the gel permeation chromatography (GPC) method using polystyrene as a standard substance. Refers to a low molecular weight component with a number average molecular weight of 1/3 or less of the number average molecular weight (Mn), and peaks at 1/3 of the number average molecular weight (Mn) calculated when measuring the baseline and molecular weight distribution. The area% of the low molecular weight component can be obtained by dividing.

<Characteristics of polyalkylene oxide>
When a bifunctional polyalkylene oxide (A1) or a trifunctional or higher functional polyalkylene oxide (A2) is used alone as the active hydrogen-containing compound (A), the degree of unsaturation is 0.010 meq / g or less. .. It is preferably in the range of 0.002 to 0.009 meq / g, and more preferably in the range of 0.004 to 0.008 meq / g.

When a bifunctional polyalkylene oxide (A1) and a trifunctional or higher functional polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A), the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are used. It is preferable that each degree of unsaturation is within the above range, but it can be preferably used as long as the degree of unsaturation of the polyalkylene oxide having a higher content is within the above range.

Polyurethane obtained by using a polyalkylene oxide having a high degree of unsaturation exceeding 0.010 meq / g does not cure well and a large amount of migration components are generated, resulting in poor stain resistance, and it takes time to cure and workability is required. It is difficult to use due to the deterioration of. Furthermore, a large amount of low molecular weight monool is produced as a by-product, which causes a decrease in the number average molecular weight, which makes it difficult to increase the molecular weight of the polyalkylene oxide and also makes it difficult to obtain a polyalkylene oxide having a narrow molecular weight distribution. ..

In the present invention, the "unsaturation degree (meq / g)" of the polyalkylene oxide is the total amount of unsaturated groups contained in 1 g of the polyalkylene oxide, and is the method specified in JIS K1557 6.7. It is a value measured according to. The degree of unsaturation of polyalkylene oxide is an index of the amount of monool present in polyalkylene oxide, and the viscosity decreases as it increases, but the average number of functional groups of polyalkylene oxide may decrease, so it is used as a raw material for polyurethane. At that time, a stop reaction may occur, leading to a decrease in the molecular weight of polyurethane and an increase in uncrosslinked low molecular weight components, or acting as a dungling chain in polyurethane, which may reduce curability.

In the present invention, the number average molecular weight (M) calculated from the OHV of the more component of the polyalkylene oxide (A1) or the polyalkylene oxide (A2) is 1000 or more. It is preferably in the range of 1000 to 7000, and more preferably in the range of 1000 to 4000.

When the number average molecular weight (M) of the larger component of the polyalkylene oxide (A1) or the polyalkylene oxide (A2) is less than 1000, the difference in the degree of unsaturation and the molecular weight distribution becomes small, and the curable resin composition is applied. The remarkable effect of improving the property and improving the contamination of the cured product cannot be obtained.

On the other hand, the number average molecular weight (M) calculated from the OHV of the polyalkylene oxide (A2) is not particularly limited, but is preferably in the range of 1000 to 30,000, more preferably in the range of 1000 to 7000, and even more preferably. Is in the range of 1000-4000.

In the present invention, the number average molecular weight (M) calculated from the OHV of the polyalkylene oxide is a value calculated using the following mathematical formula (4) based on the hydroxyl value (OHV, unit is mgKOH / g) of the polyalkylene oxide. Say.

Here, "OHV" is a value measured in accordance with JIS K1557 6.4. The "number of hydroxyl groups per molecule" refers to the number of active hydrogen atoms per molecule of the active hydrogen-containing compound, which is an initiator used as a raw material in producing the polyalkylene oxide (A). If the number of active hydrogen atoms in the initiator cannot be specified in a commercially available product, the nominal number of functional groups is used.

In the present invention, the polyalkylene oxide (A1) used as the active hydrogen-containing compound (A) is a liquid in a room temperature environment, and an amorphous compound is preferable. If it is liquid and amorphous in a room temperature environment, it is easy to use without heating and has excellent moldability.

The glass transition temperature of the polyalkylene oxide (A1) is preferably −30 ° C. or lower because it is easy to handle and the low temperature characteristics of the curable resin composition are likely to be good.

The viscosity of the polyalkylene oxide (A1) used as the active hydrogen-containing compound (A) under 25 ° C. conditions is not particularly limited and may be appropriately selected depending on the intended use, but is preferably 0.1 to 2000 Pa · s (25 ° C.). It is in the range, more preferably 0.2 to 200 Pa · s (25 ° C.). If the viscosity of the polyalkylene oxide (A1) is in the range of 0.1 to 2000 Pa · s (25 ° C.), it is easy to mold and it is easy to control the physical properties of the cured product.

In the present invention, the "viscosity" under the condition of 25 ° C. refers to a value measured by a cone plate rotational viscometer according to JIS K1557-5 6.2.3. Specifically, it refers to the viscosity under the condition of a shear rate of 0.1 (1 / s), but if the viscosity does not fall within the measurement range, the shear rate range is set to 0.01 to 10 (1 / s) so as to fall within the measurement range. ) May be adjusted.

In the present invention, when the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A1), the amount of the polyalkylene oxide (A1) added is as long as the gist of the present invention is not impaired. Although not particularly limited, it is preferably in the range of 0.5 to 250 parts by weight, and more preferably in the range of 5 to 130 parts by weight with respect to 100 parts by weight of the polyalkylene oxide (A1). Among them, when the degree of unsaturation of the polyalkylene oxide (A2) exceeds 0.029 meq / g, or when the molecular weight distribution thereof exceeds 1.069, the polyalkylene oxide (A1) is 100 parts by weight. The range of A2) is preferably less than 20 parts by weight, and more preferably less than 10 parts by weight.

When the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are used in combination as the active hydrogen-containing compound (A), a polyalkylene oxide mixture in which the polyalkylene oxide (A1) and the polyalkylene oxide (A2) are combined. it is preferred that the average functionality _{f ave} of is in the range of 2.01 to 3.00. And it decreases the value of the average functionality _{f ave} is too low elastic modulus, since the adhesive tends to decrease, more preferably in the range of 2.01 to 2.80, most preferably 2.19 to 2. It is in the range of 70.

In the present invention, the average number of functional groups _fave as a polyalkylene oxide mixture obtained by combining the polyalkylene oxide (A1) and the polyalkylene oxide (A2) is a value calculated from the following formula (5).

_{Here, f A1} is average functionality polyalkylene oxide _{(A1), W} A1 is parts by weight of polyalkylene oxide _{(A1), M} A1 represents a number average molecular weight of the polyalkylene oxide _{(A1), f A2} poly average functionality of the alkylene oxide _{(A2), W} A2 is parts by weight of the alkylene oxide _{(A2), M} A2 represents a number average molecular weight of the polyalkylene oxide (A2).

The average number of functional groups of the present invention does not take into account the substantial decrease in the number of functional groups due to the by-produced monool, and the diol obtained by using the bifunctional initiator is obtained by using a few functional initiators. The resulting triol can be calculated as 3.

Further, as the active hydrogen-containing compound (A), polyalkylene oxide (A1), such as polytetramethylene glycol, polyester polyol, chain extender such as low molecular weight diol and low molecular weight diamine, as long as the gist of the present invention is not impaired, Other active hydrogen-containing compounds other than A2) may be contained. The content of the other active hydrogen-containing compound is preferably less than 50 parts by weight with respect to 100 parts by weight of the polyalkylene oxide having a larger content among the polyalkylene oxides (A1) and (A2). It is preferably in the range of less than 5 parts by weight, and most preferably not contained.

<Manufacturing of polyalkylene oxide>
In the present invention, the method for producing the polyalkylene oxide (A1) is not particularly limited, but for example, ring-opening polymerization of the alkylene oxide is carried out in the presence of an active hydrogen-containing compound, a base catalyst and a Lewis acid. Can be manufactured by

For example, when an active hydrogen-containing compound and a base catalyst are mixed and treated under reduced pressure to prepare a catalytically active species precursor, sufficient water and solvent are removed.
Furthermore, when Lewis acid is mixed and treated under reduced pressure to prepare a catalytically active species, by-products are sufficiently removed, and by selecting a specific Lewis acid that is a by-product with a low boiling point, it is a factor to widen the molecular weight distribution. Suppressing the polyalkylene oxide derived from Lewis acid,
Through the manufacturing process of adding an alkylene oxide using a catalyst that combines a base catalyst with few side reactions and a specific Lewis acid,
Use alkylene oxide with a low water content of 100 ppm or less,
However, the production is not particularly limited.

The method for producing the polyalkylene oxide (A2) is not particularly limited, and the polyalkylene oxide (A2) can be produced by a conventionally known production method. For example, an alkylene oxide is added to a trifunctional or higher functional initiator to a predetermined molecular weight using a cesium metal compound catalyst, a composite metal cyanide complex catalyst, a phosphazene catalyst, an imino group-containing phosphazenium salt catalyst, a barium hydroxide catalyst, or the like. There is a way to do it.

A low-viscosity polyalkylene oxide (A2) having a low degree of unsaturation and a narrow molecular weight distribution can be easily obtained, and the curable resin composition containing a urethane prepolymer using the polyalkylene oxide (A2) can be easily handled and the obtained cured urethane product can be improved. Since it tends to have excellent stain resistance, it is preferably produced by ring-opening polymerization of an alkylene oxide in the presence of an active hydrogen-containing compound, a base catalyst such as an imino group-containing phosphazenium salt, and a Lewis acid catalyst.

The base catalyst is not particularly limited, but it is preferable to use a catalyst system in which a base catalyst and Lewis acid are used in combination because the applicable range of the alkylene oxide is wide, the polymerization activity is high, and the degree of unsaturation tends to be low.

Here, the Lewis acid is not particularly limited, and examples thereof include an aluminum compound, a zinc compound, and a boron compound. Among these, organoaluminum, aluminoxane, and organozinc are preferable, and organoaluminum is more preferable, because it is an alkylene oxide polymerization catalyst having excellent catalytic performance.

Examples of the aluminum compound include trimethylaluminum, triethylaluminum, triisobutylaluminum, trinormalhexylaluminum, triethoxyaluminum, triisopropoxyaluminum, triisobutoxyaluminum, triphenylaluminum, diphenylmonoisobutylaluminum, monophenyldiisobutylaluminum and the like. Organic aluminum; aluminoxane such as methylaluminoxane, isobutylaluminoxane, methyl-isobutylaluminoxan; inorganic aluminum such as aluminum chloride, aluminum hydroxide, aluminum oxide can be mentioned.

Among these, trimethylaluminum, triethylaluminum, which have a low boiling point of 100 ° C. or less for the preparation of catalytically active species, are easy to remove, and easily suppress polyalkylene oxide derived from Lewis acid, which is a factor to widen the molecular weight distribution. Triisobutylaluminum, trinormalhexylaluminum, triethoxyaluminum, triisopropoxyaluminum and the like are preferable. The compound produced as a by-product during the preparation of catalytically active species can be determined from the structure of Lewis acid. For example, in trimethylaluminum, methane in which H is added to the methyl group of the substituent on aluminum, and in triisobutylaluminum, isobutyl of the substituent on aluminum. Isobutane with H added to the group and triisopropoxyaluminum are isopropanol with H added to the isopropoxy group.

Examples of the zinc compound include organic zinc such as dimethyl zinc, diethyl zinc and diphenyl zinc; and inorganic zinc such as zinc chloride and zinc oxide.

Examples of the boron compound include triethylborane, trimethoxyborane, triethoxyborane, triisopropoxyborane, triphenylborane, tris (pentafluorophenyl) borane, trifluoroborane and the like.

The base catalyst is not particularly limited, but a base compound having a PN bond is desirable. More preferably, it is a base compound having an imino group and a PN bond, and examples thereof include an iminophosphazenium salt compound represented by the following general formula (3) (see, for example, Japanese Patent Application Laid-Open No. 2011-132179). ..

[In the above general formula (3), R ₁ and R ₂ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. R ₁ and R ₂ may be bonded to each other to form a ring structure, or R ₁ may be bonded to each other or R ₂ may be bonded to each other to form a ring structure. X ⁻ represents a hydroxy anion, an alkoxy anion having 1 to 4 carbon atoms, a carboxy anion, an alkyl carboxy anion having 2 to 5 carbon atoms, or a hydrogen carbonate anion. ]
The ratio of the base catalyst to the Lewis acid is not particularly limited and is arbitrary as long as the action as an alkylene oxide polymerization catalyst is exhibited. For example, the base catalyst: Lewis acid = 1: 0.002 to 500 (mol). Ratio).

The polymerization temperature for producing the polyalkylene oxide used in the present invention is not particularly limited, but is in the range of 70 to 150 ° C. because the polyalkylene oxide is decomposed and the molecular weight distribution is difficult to spread and the catalytic activity is easily exhibited. It is preferably, more preferably in the range of 90 to 110 ° C.

The polymerization pressure for producing the polyalkylene oxide used in the present invention is not particularly limited, but is in the range of 0.05 to 1.0 MPa, preferably 0.1 to 0.6 MPa.

The stirring speed at the time of producing the polyalkylene oxide used in the present invention is not particularly limited and depends on the shape and internal volume of the polymerization vessel, the shape of the stirring blade, etc., but a cylindrical polymerization vessel having an internal volume of 2 L and an anchor type. In the case of a stirring blade, it is preferable to sufficiently stir at 300 rpm or more.

When adding an alkylene oxide to an active hydrogen-containing compound using a catalyst that combines an iminophospazenium salt and a Lewis acid, the iminophospazenium salt (including its precursor), Lewis acid, and an active hydrogen-containing compound At the same time, a method of preparing a catalytically active species by heating / depressurizing treatment, etc., and a method of mixing one of these components with the other two components and performing heating / depressurizing treatment, etc. to prepare a catalytically active species. , A method of preparing a catalytically active species by mixing two of these components with the other one component and performing heat / decompression treatment, etc., and mixing two of these components and performing heat / decompression treatment, etc. to perform catalytic activity. Any method may be used, such as a method in which the seed precursor is prepared, the other one component is mixed, and further heating / reducing pressure treatment is performed to prepare a catalytically active species. Of these, by-products and impurities are easily removed and a polyalkylene oxide having a narrow molecular weight distribution can be easily obtained. Therefore, preferably, an iminophosphazenium salt and an active hydrogen-containing compound are mixed and then heated and depressurized. After that, it is preferable to go through a production process in which Lewis acid is mixed and further heated / reduced pressure treatment is performed to prepare a catalytically active species and alkylene oxide is added.

The temperature of the heating / depressurizing treatment at that time is preferably 100 ° C. or higher, more preferably 100 to 130 ° C., because by-products and impurities are easily removed and a polyalkylene oxide having a narrow molecular weight distribution can be easily obtained. The pressure during the heating / depressurizing treatment is preferably less than 0.5 kPa, more preferably 0.001 to 0.2 kPa, because by-products and impurities are easily removed and a polyalkylene oxide having a narrow molecular weight distribution can be easily obtained. is there. The heating / depressurizing treatment time at that time may be 2 hours or more after mixing the iminophosphazenium salt and / or its precursor, Lewis acid, and an active hydrogen-containing compound, although it varies depending on the shape of the reaction vessel and the like. Preferably, more preferably, iminophosphazenium salt and / or a precursor thereof and an active hydrogen-containing compound are added to heating and distillation under reduced pressure for 2 hours or more after mixing, and after mixing with Lewis acid, further heating and distillation under reduced pressure for 2 hours or more. It is preferable to do so. Further, in order to remove impurities, a dehydrating solvent having a low boiling point may be added and an azeotropic operation may be performed to remove impurities.

The polyalkylene oxide used in the present invention is not particularly limited, but is preferably one in which the catalyst is removed after polymerization because the viscosity may increase if the catalyst remains. The amount of the catalyst residue of the polyalkylene oxide is preferably 200 ppm or less, more preferably 100 ppm or less. Here, the amount of catalyst residue refers to the total amount of catalyst residue when two or more types of catalysts are used in combination.

<Polyisocyanate>
In the present invention, the polyisocyanate (B) is not particularly limited, and examples thereof include compounds having at least two isocyanate groups.

Specifically, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalenedi isocyanate, trizine diisocyanate, xylylene diisocyanate. , 1,3-phenylenediocyanate, 1,4-phenylenediocyanate, lysine diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, 1,6-hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1 , 4-Cyclohexanediisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, pentamethylene diisocyanate, norbornandiisocyanate, lysine ester triisocyanate, 1,6,11-undecantry Isocyanates, 1,8-diisocyanate-4-isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, trimethylhexamethylene diisocyanate, isocyanate-containing prepolymers produced by the reaction between them and polyols, and these. A mixture of two or more kinds is exemplified. Further, modified products of these isocyanates (for example, modified products containing urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, imide group, uretonimine group, uretdione group or oxazolidone group) and Condensations such as polymethylene polyphenylene polyisocyanate (Polymeric MDI) (sometimes referred to as polynuclears) are also included.

Among these, polymethylene polyphenylene polyisocyanate (polymeric MDI), 2,4-tolylene diisocyanate, and 2,6-tolylene diisocyanate, because it is easy to obtain a curable resin composition having excellent productivity and curability. Isocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalenediocyanate, trizine diisocyanate, xylylene diisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-bis ( Isocyanatomethyl) cyclohexane, pentamethylene diisocyanate, prepolymers containing these isocyanate groups, modified products of these isocyanates (eg, urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, An imide group, a uretonimine group, a uretdione group or an oxazoridone group-containing modified product) and the like are preferable.

In addition, because of its excellent flexibility, 1,6-hexamethylene diisocyanate and modified products of these isocyanates (for example, urethane group, carbodiimide group, allophanate group, urea group, burette group, isocyanurate group, amide group, imide group) , Uretonimine group, uretdione group or oxazolidone group-containing modified product) and the like can be preferably used. These isocyanates may be used alone or in admixture of two or more.

Examples of the isocyanate-containing prepolymer include a reaction product of a monool such as polyoxyalkylene monoalkyl ether, isotridecanol, hexyldecanol, ethylhexanol, and butyltetraglycol, a polyol, a monoamine, or a polyamine with the corresponding isocyanate. Can be mentioned.

The number of functional groups of the polyisocyanate (B) (the number of NCO functional groups in one molecule) is not particularly limited, but is preferably 2 to 6 functional groups, and more preferably 2 to 3 functional groups.

As the amount of the polyisocyanate (B) added, the ratio of the total amount of NCO groups contained in the polyisocyanate (B) to the total amount of OH groups contained in the active hydrogen-containing compound (A) (described as NCO / OH ratio) is 1.713 to 1. It is a range of the addition amount to be 0.0 (molar ratio). It is preferably in the range of 2.1 to 3.0.

If the NCO / OH ratio is less than 1.71, the curable resin composition thickens and the desired adhesiveness is difficult to develop, making it difficult to use in adhesive applications. Especially, if it is less than 1.0, curing is insufficient. Therefore, it is difficult to use it for this purpose.

The amount of the polyisocyanate (B) used is not particularly limited as long as it does not impair the gist of the present invention, but is preferably the polyalkylene oxide (A1) or (A2) having the larger content. It is in the range of 0.5 to 200 parts by weight, more preferably 5 to 70 parts by weight, and most preferably 10 to 50 parts by weight with respect to 100 parts by weight of the oxide.

<NCO group-terminated urethane prepolymer>
In the present invention, the NCO group-terminated urethane prepolymer used in the curable resin composition is, for example, an NCO group-terminated urethane prepolymer which is a reaction product of the above-mentioned active hydrogen-containing compound (A) and polyisocyanate (B). Examples thereof include compounds having one or more of. Its properties are preferably liquid.

In the present invention, the content of the NCO group-terminated urethane prepolymer in the curable resin composition is not particularly limited, but is in the range of 20 to 99.9% by weight in the curable resin composition. Is more preferable, and the range is more preferably 41 to 99.9% by weight, and most preferably 65 to 99.9% by weight.

In the present invention, the number average molecular weight of the NCO group-terminated urethane prepolymer in terms of standard polystyrene is not particularly limited, but is preferably in the range of 1000 to 100,000 because it has an appropriate viscosity and is easy to handle. More preferably, it is in the range of 1000 to 40,000. Here, the number average molecular weight in terms of standard polystyrene is measured by GPC (gel permeation chromatography) under the conditions of a column temperature of 40 ° C., a flow velocity of 1.0 ml / min, and a solvent THF, and is a third-order approximation using standard polystyrene. It can be calculated as a curve calibration curve.

In the present invention, the viscosity of the NCO group-terminated urethane prepolymer is not particularly limited, but since the workability tends to be good, 1000 to 200,000 mPa. The range is preferably in the range of s, more preferably in the range of 3000 to 100,000 mPa · s.

In the present invention, the method for synthesizing the NCO group-terminated urethane prepolymer is not particularly limited, and for example, in the presence of the above-mentioned active hydrogen-containing compound (A) and polyisocyanate (B), and the additive (C) described later. Examples thereof include a method of causing a urethanization reaction. Therefore, the curable resin composition containing the obtained NCO group-terminated urethane prepolymer may contain the additive (C).

The reaction temperature when synthesizing the urethane prepolymer is not particularly limited, but is preferably in the range of 50 ° C. to 130 ° C.

<Fillers and additives>
The curable resin composition used in the present invention contains one or more selected from the group consisting of the filler (C) and the additive (D).

The filler (C) is not particularly limited, and for example, any filler such as an inorganic filler, an organic filler, and a fibrous filler can be selected and used.

Specifically, silica such as fumed silica, precipitated silica, crystalline silica, molten silica, dolomite, silicic anhydride, hydrous silicic acid, fatty acid-treated calcium carbonate, heavy calcium carbonate, and calcium carbonate such as collagen carbonate. , Carbon black, magnesium carbonate, magnesium hydroxide, iron oxide, zinc oxide, siliceous soil, calcined clay, clay, talc, titanium oxide, barium sulfate, kaolin, zeolite, bentonite, organic bentonite, aluminum, flint powder and other pigments, Examples thereof include silas balloon, glass microballoon, phenol resin / vinylidene chloride resin, polyvinyl chloride / polymethyl methacrylate, synthetic resin powder such as polystyrene, asbestos, glass fiber, glass filament and the like. Such a filler may be used alone or in admixture of two or more, and may be surface-treated with an appropriate surface treatment agent.

Among these, from the viewpoint of stainability, elasticity, and durability of the obtained cured product, it is preferably an inorganic filler, and specifically, fumed silica, precipitated silica, crystalline silica, molten silica, and the like. Silica such as dolomite, silicic anhydride, hydrous silicic acid, calcium carbonate such as fatty acid-treated calcium carbonate, heavy calcium carbonate, and collagen carbonate, carbon black, magnesium carbonate, magnesium hydroxide, iron oxide, zinc oxide, silica soil, Pigments such as calcined clay, clay, talc, titanium oxide, barium sulfate, kaolin, zeolite, bentonite, organic bentonite, aluminum and flint powder are exemplified as suitable inorganic fillers.

When the filler is used, the content thereof is not particularly limited, but is preferably in the range of 0.1 to 80% by weight, more preferably 20 to 80% by weight in the curable resin composition from the viewpoint of physical properties of the cured material. It is in the range of% by weight.

Examples of the additive (D) include urethanization catalysts, light stabilizers, antioxidants, plasticizers, solvents, leveling materials, thixotropy agents, foam stabilizers, defoamers, flame retardants, foaming agents, and release agents. Examples thereof include molds, latent curing agents, antistatic agents, silane coupling agents and the like. It is preferable to contain any one or more of these additives, and more preferably two or more of these additives are contained.

The additive (D) is appropriately selected depending on the intended use and required physical properties. For example, a light stabilizer and an antioxidant are preferably used because they can easily maintain long-term stain resistance of the cured product.

The antioxidant is not particularly limited, and examples thereof include compounds having an effect of suppressing oxidation of polymer chains such as thioether compounds, phosphorus antioxidants, and hindered phenol compounds, and the trade name is Ciba. Irganox manufactured by the company and Adeka Sulfide manufactured by Adeka.

Among them, a hindered phenol-based antioxidant is preferable as the antioxidant, and since it is easy to obtain antioxidant properties against urethane, 2,6-di-t-butyl-4-methylphenol (BHT), Ciba Japan It is particularly preferable to use one or more antioxidants selected from IRGANOX-1010, IRGANOX-1024, IRGANOX-1035, IRGANOX-1076, and IRGANOX-1081.

The light stabilizer is not particularly limited, but for example, a benzotriazole-based compound, a triazine-based light stabilizer, a benzophenone-based light stabilizer, an ultraviolet absorber such as a benzoate-based compound, a hindered amine-based light stabilizer, etc. Examples of compounds have the effect of imparting sex, etc., and the trade name is Ciba Japan's Chinubin.

Among them, as the light stabilizer, it is preferable to use one or more selected from chinubin 234, chinubin 144, chinubin C353, and chinubin B75. These antioxidants and light stabilizers can also be mixed and used.

Further, a urethanization catalyst is preferably used because it exhibits high curability and tends to improve workability.

Examples of the urethanization catalyst include organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctate, and tin 2-ethylhexanoate, iron compounds such as iron acetylacetonate and iron chloride, and lead octylate. Examples thereof include lead compounds, bismuth compounds such as bismuth octylate, tertiary amine-based catalysts such as triethylamine and triethylenediamine, and one or more catalysts selected from organotin compounds, lead octylate and bismuth octylate are preferable. ..

In addition, a plasticizer is preferably used in order to develop flexibility and enhance the followability to the substrate.

The plasticizer is not particularly limited, and for example, phthalic acid esters, non-aromatic dibasic acid esters, aliphatic esters, polyalkylene glycol esters, phosphoric acid esters, trimellitic acid esters, etc. Examples thereof include chlorinated paraffins, hydrocarbon oils, process oils, polyethers, epoxy plasticizers, polyester plasticizers and the like, and phthalates are preferable. Specifically, dibutyl phthalate, diheptyl phthalate, di (2-ethylhexyl) phthalate, dioctyl phthalate, dioctyl adipate, dioctyl sebacate, dibutyl sebacate, isodecyl succinate, tricresyl phosphate, tributyl phosphate, epoxidized soybean oil. , Benzyl epoxy stearate and the like.

Such plasticizers can be used alone or in admixture of two or more, or may be added during the production of the urethane prepolymer.

In addition, a solvent is preferably used because the viscosity is lowered and the workability is improved.

As a solvent, it is used for the purpose of diluting to lower the viscosity of the curable resin composition and improving workability. For example, acetone, methyl ethyl ketone, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, dipropyl ether. , N-hexane, n-heptane, toluene, xylene, cyclohexane, petroleum-based solvents such as mineral spirit and the like.

Of these, methyl ethyl ketone, ethyl acetate, toluene, mineral spirit and the like are preferable from the viewpoint of workability.

The foam stabilizer is not particularly limited, and examples thereof include silicone compounds. The defoaming agent is not particularly limited, and examples thereof include silicone compounds. The flame retardant is not particularly limited, and examples thereof include phosphorus compounds such as trischloropropyl phosphate and chlorine compounds. The release agent is not particularly limited, and examples thereof include silicone compounds. The latent curing agent is not particularly limited, and examples thereof include an aldimine compound, an oxime compound, ketimine, and oxazolidine. The thixotropy agent is not particularly limited, and examples thereof include urea derivatives such as fatty acid amide and BYK410.

When the additive (D) is used, the content thereof is not particularly limited, but preferably, each component of the additive is in the range of 30% by weight or less in the curable resin composition of the present invention. It is more preferably in the range of 15% by weight or less, and most preferably in the range of 0.5% by weight or less. When a urethanization reaction catalyst is used, it is preferably used in the range of 0.0001 to 1% by weight, more preferably 0.001 to 0.1% by weight of the curable resin composition.

The curable resin composition of the present invention may contain an isocyanate compound other than the NCO group-terminated urethane prepolymer, preferably less than 30% by weight in the curable resin composition, as long as the purpose is not impaired. It is in the range of, and more preferably not included.

<Curable resin composition>
The curable resin composition used in the present invention is preferably in the form of a liquid or a paste.

In the curable resin composition used in the present invention, the active hydrogen-containing compound (A) and the polyisocyanate (B) are prepolymerized at an arbitrary timing, and the filler (C) and the additive (D) are formed at an arbitrary timing. Can be mixed and manufactured. For example, in addition to the prepolymer method for preparing a curable resin composition by mixing and prepolymerizing the active hydrogen-containing compound (A) and the polyisocyanate (B), the active hydrogen-containing compound (A), and the polyisocyanate (B). Further, a one-shot method in which a curing agent is mixed to prepare a curable resin composition in the system and the curing is performed can be mentioned, but the prepolymer method is preferable from the viewpoint of workability and stability of physical properties.

Specifically, the active hydrogen-containing compound (A), the polyisocyanate (B), and if necessary, the additive (D) are prepolymerized in the presence of a urethanization catalyst, and further, the filler (C) and the additive (D) are formed. ) To prepare a curable resin composition, the active hydrogen-containing compound (A) and the polyisocyanate (B) are reacted in the presence of the filler (C) and the additive (D) to form an NCO group. A method for preparing a curable resin composition containing a terminal urethane prepolymer, an active hydrogen-containing compound (A) and a polyisocyanate (B) are mixed, and a filler (C) and an additive (D) are mixed during the prepolymerization. ) Is added to allow the reaction to proceed. The order and method of adding these are arbitrary and are not particularly limited. The additive (C) may be used as a masterbatch.

The active hydrogen-containing compound (A), filler (C), and additive (D) used in the curable resin composition are preferably dehydrated by vacuum heating or the like, but are dehydrated in terms of workability and curability. You may use it without it.

As a method for preparing the curable resin composition, for example, various dispersion methods that are uniformly dispersed can be used. As the stirrer, a general-purpose stirrer, a disperser, a dissolver, a kneader, a mixer, a lab plast mill, a planetary mixer, or the like can be used. Is preferable. Stirring and mixing may be carried out under nitrogen, or while heating or defoaming under reduced pressure, if necessary.

The above-mentioned curable resin composition can be suitably used as an adhesive composition from the viewpoint of workability and foam resistance.

<Adhesive composition>
The above-mentioned curable resin composition can form an adhesive cured product composed of one liquid of the curable resin composition or two or more liquids with a curing agent by reacting with various active hydrogen-containing compounds.

The one-component type includes a one-component moisture-curing type that cures by reacting with moisture in the air, and a one-component latent curing agent type that cures with an active hydrogen-containing compound obtained from a latent curing agent (1.5-component type). (Sometimes referred to as), etc.), and in the case of two or more liquids, a two-component curing type in which a main agent containing a curable resin composition and a curing agent or other auxiliary materials are mixed and cured can be mentioned. It can be selected and used according to its characteristics.

The adhesive composition of the present invention is preferably a one-component type because it forms a uniform composition, is cured, and is easily excellent in foaming resistance.

Here, examples of the active hydrogen-containing compound include the above-mentioned moisture in the air, a curing agent, a deprotected body of a latent curing agent, and the like.

The curing agent may contain at least one compound having one or more active hydrogen groups, and is not particularly limited. For example, water, polypropylene glycol, polyethylene propylene glycol, ethylene glycol (EG), diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol (1,4-BD), 1, Diols such as 6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, and 1,4-dihydroxycyclohexane, polypropylene triol, polyethylenepropylene triol, glycerin, trimethylolpropane (TMP), triethanolamine, etc. Modified with triols, polypropylene tetraol, polyethylene propylene glycol, castor oil, shoecrose, tetrafunctional or higher functional polyols such as sorbitol, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), aniline, etc. Modified polyamines such as modified MOCA, aromatic amines such as toluenediamine, diphenylmethanediamine, diethyltoludiamine, aliphatic amines such as ethylenediamine, polyamines such as Jeffamine ED, aminoalcohols such as ethanolamine and diethanolamine, and two of these. Examples include a mixture of more than seeds. Examples of the curing agent combination system include a MOCA-polyol combination curing agent in which an aromatic amine is mixed with polyalkylene oxide.

Among them, polyalkylene oxides such as polypropylene polyols and polyethylene propylene polyols are easy to develop sufficient curability and appropriate pot life, and easily develop mechanical properties and durability of the obtained urethane cured product. , 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), modified polyamines such as modified MOCA modified with aniline, MOCA modified with tolylenediisocyanate, metaxylylenediamine, toluenediamine, MOCA-polyol. It is preferably at least one selected from the group consisting of the combined curing agent.

When producing a two-component curing type adhesive composition, the volume ratio of the main agent to the curing agent solution is 1 by using it as a curing agent solution in which the filler (C) and the additive (D) are added to the curing agent. : It is easy to control in the range of 0.2 to 3, the work error is reduced, the workability is improved, and the variation in the composition is reduced, so that it becomes easy to obtain a low-contamination two-component curable adhesive composition.

When a polyalkylene oxide such as polypropylene polyol or polyethylene propylene polyol is used as a curing agent, it is easy to obtain a urethane resin having remarkably good stain resistance. Therefore, the degree of unsaturation of the polyalkylene oxide is 0.010 meq / g or less and the molecular weight is 0.010 meq / g or less. It is in the range of 500 to 10000, and is preferably a 2- to 4-functional polyalkylene oxide synthesized by using a base catalyst and a Lewis acid catalyst in combination.

If necessary, the curing agent may contain a wetting dispersant, a solvent, a leveling material, an antioxidant, an antioxidant, a light stabilizer, a filler, a plasticizer and the like.

The amount of the curing agent added is in the range in which the equivalent ratio (NCO / RH) of the NCO group contained in the main agent containing the curable resin composition to the active hydrogen group contained in the curing agent is 0.7 to 2.0. It is preferable to add with. More preferably, it is added in a range where NCO / RH is 1.0 to 1.5. The amount of the curing agent added is preferably in the range of 20 to 300 parts by weight with respect to 100 parts of the main agent containing the curable resin composition because the workability is easily excellent.

Using the adhesive composition of the present invention, coating with a spatula, comb, roller, iron, rake, etc., extrusion with a sealing gun, spraying, etc., coating film with any thickness by hand coating or machine coating It can have any shape such as a film sheet, a thick material, or the like. It is also possible to blend a compound having a sagging property and coat an elevation, a wall surface, a surface, a depression or the like with a roller, a ricin gun, an airless gun or the like to form a coating film or a cured product.

Since the adhesive composition of the present invention is easily curable, it can be made into a thick shape, and because it is excellent in physical properties, it can be made into a low-thickness shape and a wide range of shapes.

The adhesive composition of the present invention is characterized by excellent stain resistance, and any one-component moisture-curing type, two-component curing type, or 1.5-component type can be suitably used.

The specific use of the adhesive composition of the present invention is not particularly limited, but is, for example, an adhesive for flexible packaging, an adhesive for civil engineering and construction, a bedrock coagulant, an adhesive for floors, and a vehicle. Adhesives, elastic adhesives, structural adhesives and the like.

Examples of the method for applying the adhesive of the present invention include a method in which the adhesive is directly applied to a washed substrate, dried as necessary, and the adherends are adhered and cured.

Examples of the elastic adhesive include a method of extruding a curable resin composition between the adherends and curing the adhesive to bond the adhesive.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention will not be construed as being limited to the following Examples as long as the gist of the present invention is not exceeded. The raw materials used in the following Examples and Comparative Examples and the evaluation method are as shown below.

(material)
<Polyprethane>
Table 1 also shows the properties of the polyol used in Examples or Comparative Examples.

Polyol (A1): propylene that has been sufficiently dehydrated and desolvated in combination with an imino group-containing phosphazenium salt (IPZ) catalyst and triisopropoxyaluminum, and sufficiently dehydrated to polyoxypropylene glycol having a bifunctional molecular weight of 400. Bifunctional polyalkylene oxide to which oxide is added.

Polyol (A2): Commercially available general-purpose polyoxypropylene glycol (PP-2000 manufactured by Sanyo Chemical Industries, Ltd.).

Polyol (A3): A polyalkylene oxide obtained by adding propylene oxide to polyoxypropylene glycol having a bifunctional molecular weight of 400 using a composite metal cyanide complex (DMC) catalyst.

Polyol (A4): propylene that has been sufficiently dehydrated and desolvated in combination with an imino group-containing phosphazenium salt (IPZ) catalyst and triisopropoxyaluminum, and sufficiently dehydrated to polyoxypropylene glycol having a trifunctional molecular weight of 400. Bifunctional polyalkylene oxide to which oxide is added.

Polyol (A5): Commercially available general-purpose polyoxypropylene glycol (GP-4000 manufactured by Sanyo Chemical Industries, Ltd.).

Polyol (A6): A polyalkylene oxide obtained by adding propylene oxide to polyoxypropylene glycol having a trifunctional molecular weight of 1000 using a composite metal cyanide complex (DMC) catalyst.

The above polyol was heated and vacuum dehydrated before use. Except for commercially available products, the catalyst was removed and used by a conventional method.

The polyols (A1) and (A4) had a narrow degree of unsaturation and a narrow molecular weight distribution. On the other hand, the polyols (A2) and (A5) had a high degree of unsaturation, and the polyols (A3) and (A6) had a wide molecular weight distribution and a high viscosity.

<Polyisocyanate>
Polyisocyanate (C1): 4,4'-diphenylmethane diisocyanate (4,4'-MDI, Millionate MTL manufactured by Tosoh Corporation).

Polyisocyanate (C2): HDI isocyanurate (Tosoh Coronate HX).

These were used as they were without purification.

<Filler>
Filler (D1): Heavy calcium carbonate (Whiten SB manufactured by Maruo Calcium Co., Ltd.).

The above commercial product was heated and vacuum dehydrated before use.

<Additives>
Additive (E1): Hindered phenolic antioxidant (Irganox 1010 manufactured by BASF).

Additive (E2): Bismuth octylate (Pucat 25 manufactured by Nihon Kagaku Sangyo Co., Ltd.).

Additive (E3): Methyl ethyl ketone (manufactured by Wako Pure Chemical Industries, Ltd.).

The above commercially available product was used as it was.

(Evaluation method of curable resin composition)
<Hydroxy group value, number average molecular weight>
The hydroxyl value (OHV) of the polyalkylene oxide was measured according to the method of JIS-K1557-1. The number average molecular weight of the polyalkylene oxide is a value calculated using the above formula (4) based on the hydroxyl value of the polyalkylene oxide.

<Degree of unsaturation>
The measurement was performed according to the method of JIS-K1557-6.

<Molecular weight distribution (Mw / Mn)>
10 mg of polyol and 10 ml of THF were added to the sample bottle, dissolved by allowing to stand overnight, and filtered through a PTFE cartridge filter (0.5 μm) to obtain a sample. The RI detector RI8020 is connected in series as the detector, and a total of four Tskgel SuperH4000 x 2 and Tskgel SuperH3000 x 2 manufactured by Tosoh, whose separation column is filled with a filler having a particle size of 3 μm, are connected in series, and the reference side is a resistance tube. × 5 are connected, special grade tetrahydrofuran containing BHT stabilizer manufactured by Wako Co., Ltd. is used as the developing solvent, and the flow rate on the separation column side is 0.6 ml / min, the flow rate on the reference side is 0.15 ml / min, and the column temperature is 40 ° C. analyzed. The molecular weight distribution (Mw / Mn) was analyzed using a third-order approximation curve using eight standard polystyrenes manufactured by Tosoh Corporation with a known molecular weight as a calibration curve. Tosoh's HLC-8320GPC was used as the measuring device, and Tosoh's HLC-8320GPC-ECOSEC-Workstation was used for the analysis.

<Curable>
The time required for curing the curable resin composition coated to a thickness of about 200 μm was evaluated as follows. The curable resin composition during curing was collected over time, and the time required for the conversion to reach 95% with respect to the initial content of NCO groups by back titration using dibutylamine was evaluated as follows.

◯: When less than 6 hours Δ: When 6 hours or more and less than 12 hours ×: When 12 hours or more is required <Effervescent>
The polyethylene substrate is coated with an applicator to a thickness of about 200 μm, and the solvent-based product is allowed to stand in a draft at room temperature for 5 minutes to remove the solvent, and then allowed to stand at 25 ° C. and 50% RH for 1 hour. After placement, it was heated at 100 ° C. for 1 minute, and then a transparent PET having a thickness of 25 μm was laminated, and the appearance after curing for 7 days was visually evaluated.

◯: Visually uniform surface appearance ×: Bubbles remain in a part of the adhesive composition <contamination of the base material>
The curable resin composition was sandwiched between a polyethylene film and 25 μm PET, and the stainability on the polyethylene substrate after peeling after curing for 7 days was evaluated as an index of stainability. Silica sand No. 7 was sprayed on a polyethylene base material and allowed to stand for 1 minute, and the state of deposits remaining even when turned upside down was observed. The evaluation criteria were as follows.

◯: No adhesion of silica sand (less than 5% of surface area)
Δ: Slight adhesion of silica sand was observed and can be removed by tapping (remaining less than 5% of the surface area).
X: Adhesion of silica sand is observed and remains on the surface even when hit (remaining 5% or more of the surface area)
Regarding the contamination of the base material, ○ is passed, △, × are rejected, and if it is rejected, there is a concern that the components will flow out to the surrounding area where the adhesive is applied and contaminate it, so use it as an adhesive. Judged to be difficult.

<Manufacturing of curable resin composition and urethane cured product>
Table 2 also shows the properties of the NCO group-terminated urethane prepolymer used in Examples or Comparative Examples.

Example 1.
The polyol (A1) and the polyol (A4) were put into a four-port separable flask equipped with a stirring blade so as to have a weight ratio of 25:75, and dehydration was performed under reduced pressure at 100 ° C. for 2 hours. After cooling to room temperature, 100 parts by weight of ultra-dehydrated methyl ethyl ketone was added to 100 parts by weight of the polyol, and the mixture was stirred under nitrogen. HDI isocyanurate (Coronate HX manufactured by Tosoh Corporation) was put into a separable flask so that the ratio of HDI isocyanurate to the polyol (A1) and the polyol (A4) was 2.9 in the NCO / OH ratio. An NCO group-terminated urethane prepolymer solution was synthesized by stirring under nitrogen at 80 ° C. without catalyst until the consumption of NCO groups was stopped.

Irganox 1010 as an antioxidant and bismuth octylate as a catalyst were added to the obtained methyl ethyl ketone solution of the NCO group-terminated urethane prepolymer and stirred with a mechanical stirrer to obtain a curable resin composition.

Next, the obtained curable resin composition was applied onto a polyethylene substrate having a thickness of 100 μm using an applicator so that the film thickness after drying was 200 μm, and the solvent was allowed to stand in the draft for 5 minutes. After removing the above, the mixture was allowed to stand for 1 hour under the condition of 23 ° C. and 55% RH, heated at 100 ° C. for 1 minute, and then laminated with a transparent PET having a thickness of 25 μm and allowed to stand for 7 days to obtain an adhesive composition.

The curable resin composition had a high curing rate, and the obtained adhesive composition did not show foaming, and was excellent in curability and foaming resistance. Further, no bleeding was observed on the polyethylene base material after being allowed to stand for 7 days and then peeled off, and it was expected to be used as an adhesive having excellent stain resistance.

Example 2.
The ratio of polyol (A1) to polyol (A4) was changed to 40:60 , and 4,4'-MDI was changed to 2.2 in NCO / OH ratio instead of HDI isocyanurate, and the filler was filled without using a solvent. A curable resin composition was obtained by the same method as in Example 1 except that heavy calcium carbonate was used.

Next, the obtained curable resin composition was applied onto a polyethylene substrate having a thickness of 100 μm using an applicator so as to have a film thickness of 200 μm, and allowed to stand at 23 ° C. and 55% RH for 1 hour. After heating at 100 ° C. for 1 minute, transparent PET having a thickness of 25 μm was laminated and allowed to stand for 7 days to obtain an adhesive composition.

The curable resin composition had a high curing rate, and the obtained adhesive composition did not visually show foaming on the surface, and was excellent in curability and foaming resistance. Further, no bleeding was observed on the polyethylene base material after being allowed to stand for 7 days and then peeled off, and it was expected to be used as an adhesive having excellent stain resistance.

Comparative example 1.
A curable resin composition and an adhesive composition by the same method as in Example 1 except that a highly unsaturated polyol (A2) and a polyol (A5) were used instead of the polyol (A1) and the polyol (A4). Got

Since it takes time to cure the curable resin composition, foaming accompanying the reaction after laminating the surface base materials was observed, and the composition was inferior in foaming resistance and curability. Contamination is seen on the polyethylene base material after it has been peeled off after being allowed to stand for 7 days, and there is a concern that it will contaminate the surroundings when it is applied as an adhesive, so it is difficult to use it as an adhesive with such a requirement. It was something like that.

Comparative example 2.
A curable resin by the same method as in Example 1 except that polyols (A3) and polyols (A6) having a low degree of unsaturation but a wide molecular weight distribution and high viscosity were used instead of the polyols (A1) and the polyols (A4). A composition and an adhesive composition were obtained.

Although improvement is seen from Comparative Example 1, since it takes time to cure the curable resin composition, foaming due to the reaction after laminating the surface base materials is observed, and the composition is inferior in foaming resistance and curability. It was.
Contamination is still seen on the polyethylene base material after it has been peeled off after standing for 7 days, and there is a concern that it will contaminate the surroundings when it is applied as an adhesive. Therefore, use as an adhesive with such a requirement. Was difficult.

The above results are shown in Table 3.

Example 3.
Using the curable resin composition prepared in Example 1, the ABS base material and the polypropylene film were laminated and used as an adhesive composition.

After 6 hours, the adhesive composition had good adhesiveness without foaming and showed good curability. Further, the adhesive composition was excellent in stain resistance because no contamination was observed on the substrate when it was peeled off after being allowed to stand for 7 days.

Claims (6)

One or two selected from the group consisting of an NCO group-terminated urethane prepolymer which is a reaction product of an active hydrogen-containing compound (A) and a polyisocyanate (B), and a filler (C) and an additive (D). A curable resin composition containing the above.
The active hydrogen-containing compound (A) contains a bifunctional polyalkylene oxide (A1) and a trifunctional or higher functional polyalkylene oxide (A2 ) .
The bifunctional polyalkylene oxide (A1) and the trifunctional or higher functional polyalkylene oxide (A2 ) satisfy all of the following (a) to (d), and the NCO group-terminated urethane prepolymer satisfies the following (e). An adhesive composition comprising.
(A) The degree of unsaturation is 0.010 meq / g or less.
(B) The number average molecular weight calculated from the hydroxyl value (OHV) is 1000 or more.
(C) The molecular weight distribution (Mw / Mn) determined by the (GPC) method by gel permeation chromatography using polystyrene as a standard substance is 1.039 or less.
(D) The molecular weight distribution (Mw / Mn) obtained by the gel permeation chromatography (GPC) method and the number average molecular weight (M) calculated from the hydroxyl value (OHV) satisfy the following mathematical formula (1).
(E) The ratio (NCO / OH) of the total amount of NCO groups contained in the polyisocyanate (B) to the total amount of OH groups contained in the active hydrogen-containing compound (A) is 1.71 to 3.00 (molar ratio). The polyisocyanate (B) is polymethylene polyphenylene polyisocyanate (Polymeric MDI), 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1 , 5-Naphthalenediocyanate, trizine diisocyanate, xylylene diisocyanate, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, these The composition according to claim 1, wherein the composition is at least one selected from the group consisting of the isocyanate-containing prepolymer of the above and the modified products of these isocyanates. Claim 1 or claim, wherein the average number of functional groups _ave of the polyalkylene oxide mixture obtained by combining the polyalkylene oxide (A1) and the polyalkylene oxide (A2) is in the range of 2.01 to 3.00. 2. The composition according to 2. The composition according to any one of claims 1 to 3, wherein the filler (C) contains one or more inorganic fillers. Claims 1 to 2, wherein the additive (D) contains one or more selected from the group consisting of a filler, a urethanization catalyst, a light stabilizer, an antioxidant, a plasticizer, and a solvent. Item 8. The composition according to any one of Item 4. The molecular weight distribution (Mw / Mn) of polyalkylene oxide obtained by gel permeation chromatography (GPC) using polystyrene as a standard substance is obtained by connecting four columns in series, each of which is a separation column filled with a filler having a particle size of 3 μm. The composition according to any one of claims 1 to 5, wherein a resistance tube is connected to the reference side, and the molecular weight distribution is analyzed under the condition that tetrahydrofuran is used as the developing solvent.