Prepreg manufacturing method and matrix resin raw material composition

Abstract

Maintain a uniform varnish state during the impregnation process. [Solution] The prepreg manufacturing method includes an impregnation step S5 in which a matrix resin raw material composition containing a main component of the matrix resin, a curing agent, and a solvent is impregnated into a fiber substrate, and a drying step S7 in which the matrix resin raw material composition impregnated into the fiber substrate in the impregnation step S5 is dried. The main component is an epoxy resin. The curing agent is a PEG lignin derivative. The solvent includes a first solvent consisting of glycol ethers and a second solvent consisting of ethers.

Description

Technical Field

[0001] The present invention relates to a prepreg manufacturing method for manufacturing a prepreg in which a fiber base material is impregnated with a matrix resin having an epoxy resin as a main component and a PEG lignin derivative extracted from sugi using polyethylene glycol (PEG) as a curing agent, and a matrix resin raw material composition.

Background Art

[0002] Conventionally, a method for manufacturing a resin composition containing an epoxy resin and a PEG lignin derivative has been known. For example, in the manufacturing method of Patent Document 1, modified lignin chemically modified with polyethylene glycol is liquefied by treatment in a methanol solvent, mixed with an epoxy resin, and then the obtained solid is dried to remove methanol.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the matrix resin of the prepreg is required to be able to maintain a uniform varnish state in order to be sufficiently impregnated into the fiber base material. However, when using methanol as a solvent as in the manufacturing method described in Patent Document 1 above, it is difficult to sufficiently dissolve lignin, and it is difficult to maintain a uniform varnish state in the impregnation process into the fiber base material.

Means for Solving the Problems

[0005] One aspect of the prepreg manufacturing method according to the present invention includes an impregnation step of impregnating a fiber base material with a matrix resin raw material composition containing a main agent, a curing agent, and a solvent of the matrix resin, and a drying step of drying the matrix resin raw material composition impregnated into the fiber base material in the impregnation step. The main agent is an epoxy resin. The curing agent is a PEG lignin derivative. The solvent includes a first solvent composed of glycol ethers and a second solvent composed of ethers.

[0006] Another aspect of the present invention, a matrix resin raw material composition, includes a main agent, a curing agent, and a solvent. The main agent is an epoxy resin. The curing agent is a PEG lignin derivative. The solvent includes a first solvent composed of glycol ethers and a second solvent composed of ethers.

Advantages of the Invention

[0007] According to the present invention, a uniform varnish state can be maintained in the impregnation step.

Brief Description of the Drawings

[0008] [Figure 1] A flowchart showing an example of the prepreg manufacturing method according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to FIG. 1. The prepreg according to the embodiment of the present invention is an intermediate material of a fiber-reinforced resin, and is a sheet-like material in which a fiber base material such as glass fiber is impregnated with a matrix resin. By laminating and press-molding the prepregs, a fiber-reinforced resin can be manufactured. The laminated prepregs are adhered to each other by a viscous matrix resin. By press-molding the thus-laminated prepregs under temperature conditions not lower than the curing temperature of the matrix resin, the matrix resin is cured and the fiber-reinforced resin is completed.

[0010] Epoxy resins are a typical example of thermosetting resins used as matrix resins. Bio-derived PEG-lignin derivatives can be used as curing agents for epoxy resins. However, PEG-lignin derivatives are powders at room temperature and are difficult to dissolve. Therefore, in this embodiment, the matrix resin raw material composition is constructed as follows, so that the PEG-lignin derivative is dissolved using a suitable solvent and mixed with the epoxy resin to create a state suitable for impregnation into a fiber substrate.

[0011] Figure 1 is a flowchart showing an example of a prepreg manufacturing method according to an embodiment of the present invention. As shown in Figure 1, in the prepreg manufacturing method according to an embodiment of the present invention, first in step S1, 75 parts (e.g., 585 g) of powdered PEG-lignin derivative are weighed out as a curing agent. As the PEG-lignin derivative, for example, SD4 manufactured by Lignomateria as shown below can be used. [ka]

[0012] Next, in mixing step S2, 50 parts (e.g., 390 g) of liquid methyl cellosolve is weighed out as the first solvent and added to the powdered PEG-lignin derivative weighed out in step S1, and the mixture is stirred in a mixer for 2 minutes. The PEG-lignin derivative has a phenol group derived from lignin and a hydroxyl group derived from PEG. By selecting a solvent with high compatibility with the phenol group and allowing it to approach the phenol group, the PEG-lignin derivative can be sufficiently dissolved, and a varnish in a uniform mixed state can be obtained.

[0013] A solvent with high compatibility with phenol groups has a solubility parameter SP value of 14.6 [cal / cm³], which is the SP value for hydroxyl groups. 3 ] 1 / 2 Rather than the SP value of the phenol group, which is 11.5 [cal / cm³] 3 ] 1 / 2 A solvent close to this value can be selected. More specifically, a solvent with a solubility parameter SP value of 8 [cal / cm³]. 31 / 2 or more and 12.5 [cal / cm 3 1 / 2 The following solvents can be selected.

[0014] Examples of such solvents include propylene glycol monomethyl ether (CH3OCH2CH(CH3)OH) (boiling point: 120 °C) with an SP value of 11 [cal / cm 3 1 / 2 methyl cellosolve (CH3OCH2CH2OH) (boiling point: 124 °C) with an SP value of 12.1 [cal / cm 3 1 / 2 ethyl cellosolve (C2H5OCH2CH2OH) (boiling point: 136 °C) with an SP value of 8.9 [cal / cm 3 1 / 2 ethylene glycol tertiary butyl ether (CH3C(CH3)2OCH2OH) (boiling point: 152 °C) with an SP value of 10.2 [cal / cm 3 1 / 2 butyl cellosolve (C4H9OCH2CH2OH) (boiling point: 171 °C) with an SP value of 8.4 [cal / cm 3 1 / 2 3-methoxy-3-methyl-1-butanol (CH3OC(CH3)2CH2CH2OH) (boiling point: 174 °C) with an SP value of 8.2 [cal / cm 3 1 / 2 ethylene glycol monopropyl ether (CH3CH2CH2OCH2CH2OH) (boiling point: 150 °C) with an SP value of 10.2 [cal / cm 3 <00(00022>diethylene glycol monobutyl ether (C4H9O(CH2CH2O)2H) (boiling point: 230 °C) with an SP value of 8.4 [cal / cm 3 1 / 2 ] triethylene glycol monobutyl ether (C4H9O(CH2CH2O)3H) (boiling point: 271 °C) with an SP value of 8.2 [cal / cm 3 1 / 2 3 1 / 2 ​​​​​​​​​​​​​Glycol ethers such as dipropylene glycol monomethyl ether (CH3O(C3H6O)2H) (boiling point: 188°C), with an SP value of 10.2 [cal / cm³]. 3 ] 1 / 2 1,3-Dioxolane (C3H6O2) (boiling point: 75°C), SP value: 10.3 [cal / cm³] 3 ] 1 / 2 This is 1,4-dioxane (C4H8O2) (boiling point: 101℃), with an SP value of 9.3 [cal / cm³]. 3 ] 1 / 2 Ethers such as tetrahydrofuran (THF) (C4H8O) (boiling point: 66°C) can be selected.

[0015] The solvent must be evaporated and removed during the drying process before press molding. The temperature conditions for this drying process are set according to the boiling point of the solvent. The curing temperature of the matrix resin, that is, the temperature at which the curing reaction between the epoxy resin, which is the main component of the matrix resin, and the PEG-lignin derivative, which is the curing agent, begins, is approximately 140°C. In order to maintain the unreacted state of the matrix resin and its viscosity after the drying process, it is necessary to select a solvent with a boiling point lower than the curing temperature. More specifically, a solvent with a boiling point of 140°C or lower can be selected.

[0016] Examples of such solvents include glycol ethers such as propylene glycol monomethyl ether (SP value: 11 [cal / cm³]). 3 ] 1 / 2 ), methyl cellosolve (SP value: 12.1 [cal / cm³] 3 ] 1 / 2 ), ethyl cellosolve (SP value: 8.9 [cal / cm³] 3 ] 1 / 2 ), ethers 1,3-dioxolane (SP value: 10.2 [cal / cm³] 3 ] 1 / 2 ), 1,4-dioxane (SP value: 10.3 [cal / cm³] 3 ] 1 / 2 ), THF (SP value: 9.3 [cal / cm³] 3 ] 1 / 2) can be selected. Among these solvents, the SP value is particularly high, as it is the SP value of the phenol group, 11.5 [cal / cm³]. 3 ] 1 / 2 By selecting a glycol ether solvent similar to the one described, such as methyl cellosolve, as the first solvent, the PEG-lignin derivative can be sufficiently dissolved, and a varnish with a homogeneous mixture can be obtained.

[0017] Furthermore, known solvents for PEG-lignin derivatives include N,N-dimethylformamide (formyldimethylamine, DMF) (boiling point: 153°C), dimethyl sulfoxide (DMSO) (boiling point: 189°C), N-methyl-2-pyrrolidone (NMP) (boiling point: 202°C), and N,N-dimethylacetamide (DMAc) (boiling point: 165°C). However, the boiling points of these solvents are higher than the curing temperature (140°C). Also, for example, the SP value of DMSO is 14.5 [cal / cm³]. 3 ] 1 / 2 The SP value of the phenol group is 11.5 [cal / cm³]. 3 ] 1 / 2 Rather than the SP value of the hydroxyl group, it is 14.6 [cal / cm³]. 3 ] 1 / 2 It is close to that. Similarly, the SP value of methanol, which is known as a solvent for PEG-lignin derivatives, is 14.5 [cal / cm³]. 3 ] 1 / 2 This value is close to the SP value of the hydroxyl group.

[0018] Next, in the second mixing step S3, 50 parts (e.g., 390 g) of liquid THF is weighed out as the second solvent and added to the mixed composition (varnish) of the curing agent and the first solvent obtained in the first mixing step S2, and stirred in a mixer for 2 minutes. As the second solvent, glycol ethers and ethers with high compatibility with phenol groups, and ethers with relatively low boiling points, more specifically, 1,3-dioxolane (boiling point: 75°C), 1,4-dioxane (boiling point: 101°C), THF (boiling point: 66°C), etc., with boiling points of 25°C or higher and 110°C or lower, can be selected, for example, THF with a particularly low boiling point.

[0019] In this way, by adding a second solvent with a lower boiling point to a varnish, which is a mixed composition of a hardener and a first solvent, it is possible not only to further dissolve the hardener but also to dilute the first solvent and lower the boiling point of the entire solvent mixture (first and second solvents combined). If the boiling point of the entire solvent is high, the solvent may not completely evaporate depending on the temperature conditions of the drying process, and some solvent may remain after the drying process. By lowering the boiling point of the entire solvent, the solvent can be completely evaporated and removed during the drying process.

[0020] Next, in step S4, 100 parts (e.g., 780 g) of liquid epoxy resin is weighed out as the main component and added to the mixed composition (varnish) of the curing agent and solvent (first solvent, second solvent) obtained in the second mixing step S3, and stirred in a mixer for 2 minutes. As the epoxy resin, for example, sorbitol glycidyl ether such as Denacol EX-614B manufactured by Nagase ChemteX can be used. As other epoxy resins, limonene dioxide such as Celoxide 3000 manufactured by Daicel, epoxidized soybean oil such as Adekasizer O-130P manufactured by ADEKA and Sansosizer E-2000H manufactured by Shin Nippon Rika can also be used, epoxidized castor oil such as EPOX MK R151 manufactured by Printec, and epoxidized linseed oil such as Adekasizer O-180A manufactured by ADEKA and Sansosizer E-9000H manufactured by Shin Nippon Rika can also be used. In the following, the mixed composition (varnish) of the curing agent and solvent (first solvent, second solvent) and main component obtained in mixing steps S1 to S4 may be referred to as the "matrix resin raw material composition".

[0021] Next, in the impregnation step S5, one fiber substrate is immersed in the varnish, which is the matrix resin raw material composition obtained in the mixing steps S1 to S4, to impregnate the fiber substrate with varnish. As the fiber substrate, for example, glass fiber fabrics such as glass cloth, such as Nitto Boseki 7628WLA209 105BZ, can be used. In addition to glass fiber fabrics, glass fiber nonwovens, glass fiber mats, carbon fiber fabrics, carbon fiber nonwovens, carbon fiber mats, aramid fiber fabrics, aramid fiber nonwovens, aramid fiber mats, plant fiber fabrics, plant fiber nonwovens, plant fiber mats, paper, etc. can also be used as the fiber substrate.

[0022] If the entire solvent consists only of ethers with low boiling points (for example, THF with a boiling point of 66°C), the solvent may evaporate and be lost during the impregnation process S5, potentially increasing the viscosity of the varnish. If the viscosity of the varnish increases before the fiber substrate is sufficiently impregnated, the impregnation of the varnish into the fiber substrate will not proceed further, potentially resulting in areas of the fiber substrate that are not impregnated with varnish. By using a solvent that is a balanced mixture (for example, in equal amounts) of ethers with relatively low boiling points (boiling points of 25°C or higher and 110°C or lower, for example, THF with a boiling point of 66°C) and glycol ethers with relatively high boiling points (boiling points of 120°C or higher and 140°C or lower, for example, methyl cellosolve with a boiling point of 124°C), it is possible to prevent the entire amount of solvent from evaporating during the impregnation process and maintain a uniform varnish state throughout the entire impregnation process.

[0023] Next, in step S6, the fiber substrate, which has been impregnated with the matrix resin raw material composition (varnish) in the impregnation step S5, is passed between rollers with a clearance set to 0.2 mm, and excess varnish is squeezed off and removed.

[0024] Next, in drying step S7, the matrix resin raw material composition (varnish), which was impregnated into the fiber substrate in impregnation step S5 and partially removed in step S6, is dried to volatilize and remove the solvents (first solvent and second solvent). More specifically, the fiber substrate impregnated with the matrix resin raw material composition is dried in a drying oven at 120°C for 10 minutes. Once the solvents contained in the matrix resin raw material composition have volatilized and been removed, a prepreg is obtained in which the matrix resin composition, which is a mixed composition of a curing agent and a main component, is impregnated into the fiber substrate.

[0025] By using a solvent that is a balanced mixture (e.g., equal amounts) of glycol ethers with relatively high boiling points (e.g., methyl cellosolve with a boiling point of 124°C) and ethers with relatively low boiling points (e.g., THF with a boiling point of 66°C), the solvent can be evaporated and removed in a relatively short time (e.g., 10 minutes) even under relatively mild temperature conditions (e.g., 120°C). For example, at around 120°C, which is lower than the curing temperature, if the entire solvent is methyl cellosolve with a boiling point of 124°C, drying will take a long time. However, by using THF with a boiling point of 66°C as half of the solvent, the drying time can be shortened.

[0026] Next, in the lamination process S8, the prepregs obtained in the drying process S7 are laminated (for example, 10 layers). The laminated prepregs are bonded to each other by a viscous matrix resin.

[0027] Next, in the press molding process S9, the prepreg laminated in the lamination process S8 is press molded at 160°C and 2 MPa for 80 minutes. By press molding under temperature conditions above the curing temperature of the matrix resin (140°C), the matrix resin hardens, and a fiber-reinforced resin is obtained in which the laminated prepreg is integrated.

[0028] According to embodiments of the present invention, the following effects can be achieved. (1) The prepreg manufacturing method includes an impregnation step S5 in which a matrix resin raw material composition containing a main component of the matrix resin, a curing agent, and a solvent is impregnated into a fiber substrate, and a drying step S7 in which the matrix resin raw material composition impregnated into the fiber substrate in the impregnation step S5 is dried (Figure 1). The main component is an epoxy resin. The curing agent is a PEG lignin derivative. The solvent includes a first solvent consisting of glycol ethers and a second solvent consisting of ethers.

[0029] By using glycol ethers and ethers, which have high compatibility with phenol groups, as solvents for PEG-lignin derivatives, the PEG-lignin derivatives can be sufficiently dissolved, resulting in a uniformly mixed varnish. Furthermore, by using glycol ethers with relatively high boiling points and ethers with relatively low boiling points, the solvent can be evaporated relatively quickly even under relatively mild temperature conditions during the drying process, while maintaining a uniform varnish state during the impregnation process.

[0030] (2) The boiling point of the first solvent is 120°C or higher and 140°C or lower. The boiling point of the second solvent is 25°C or higher and 110°C or lower. By using a solvent whose boiling point is below the curing temperature of the matrix resin (140°C), the viscosity of the matrix resin can be maintained even after the drying process in which the solvent is evaporated and removed. Furthermore, by using a second solvent with a boiling point of 110°C or lower as part of the solvent, the solvent can be evaporated and removed in a relatively short time even in a drying process with relatively mild temperature conditions. In addition, by using a first solvent with a boiling point of 120°C or higher as part of the solvent, it is possible to prevent the entire amount of solvent from evaporating during the impregnation process and maintain a uniform varnish state throughout the entire impregnation process.

[0031] (3) The prepreg manufacturing method further includes mixing steps S1 to S4 to obtain a matrix resin raw material composition by mixing a main agent, a curing agent, and a solvent (Figure 1). Mixing steps S1 to S4 include a first mixing step S2 in which the curing agent and a first solvent are mixed, and a second mixing step S3 in which the mixed composition of the curing agent and the first solvent is mixed with a second solvent (Figure 1). Of the first solvent consisting of glycol ethers and the second solvent consisting of ethers, the SP value is 11.5 [cal / cm³], which is the SP value of the phenol group. 3 ] 1 / 2 By first mixing a first solvent that is similar to and has relatively high compatibility with phenol groups, the PEG-lignin derivative can be suitably dissolved.

[0032] (4) The main component is at least one of epoxidized soybean oil and sorbitol glycidyl ether. By using bio-resins in the main component in addition to curing agents using PEG-lignin derivatives, the utilization of bio-resins can be promoted.

[0033] (5) The first solvent is methyl cellosolve. The second solvent is THF. By using methyl cellosolve, which has particularly high compatibility with phenol groups, as the first solvent, the PEG-lignin derivative can be sufficiently dissolved, and a varnish with a uniform mixture can be obtained. Furthermore, by using THF, which has a particularly low boiling point among solvents with high compatibility with phenol groups, as the second solvent, the solvent can be evaporated and removed in a relatively short time even in a drying process under relatively mild temperature conditions.

[0034] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications with each other. [Examples]

[0035] [Example 1] In Example 1, methyl cellosolve was used as the first solvent and THF as the second solvent in the prepreg manufacturing method shown in Figure 1. In this case, it was confirmed that the varnish (matrix resin raw material composition) was transparent overall and in a uniform mixed state in which the main component and curing agent were sufficiently miscible after the completion of mixing steps S1 to S4. Furthermore, it was confirmed that the matrix resin composition was impregnated throughout the fiber substrate and in a viscous, uniform mixed state in which the main component and curing agent had not reacted. In addition, when the cross-section of the fiber-reinforced resin was observed after the completion of the press molding step S9, it was confirmed that there were no voids inside. That is, if solvent remains in the varnish after the completion of the drying step S7, voids will be created in the matrix resin of the fiber-reinforced resin as the matrix resin hardens and the residual solvent evaporates during the subsequent press molding step S9. If there are no voids inside the fiber-reinforced resin after the press molding process S9 is completed, the solvent has completely evaporated and been removed in the drying process S7.

[0036] [Example 2] In Example 2, THF was used as the first solvent and methyl cellosolve as the second solvent in the prepreg manufacturing method shown in Figure 1. In this case, some cloudiness was observed in the varnish (matrix resin raw material composition) after the mixing steps S1 to S4 were completed, but in the impregnation step S5, the varnish (matrix resin raw material composition) was impregnated into the entire fiber substrate. Furthermore, when the cross-section of the fiber-reinforced resin was observed after the press molding step S9 was completed, it was confirmed that there were no voids inside, indicating that a fiber-reinforced resin in an appropriate state could be manufactured.

[0037] [Comparative Example 1] In Comparative Example 1, the first mixing step S2 and the second mixing step S3 of the prepreg manufacturing method shown in Figure 1 were combined into a single solvent mixing step, using only THF as the solvent. Specifically, 100 parts (e.g., 780 g) of THF were weighed and added to the PEG-lignin derivative weighed in step S1, and the mixture was stirred in a mixer for 2 minutes. In this case, at the completion of the mixing steps up to step S4, the varnish (matrix resin raw material composition) was transparent throughout, confirming a uniform mixture in which the main component and the curing agent were sufficiently miscible. However, in the impregnation step S5, the solvent evaporated and was lost before the varnish (matrix resin composition) could impregnate the entire fiber substrate, increasing the viscosity of the varnish and preventing the entire fiber substrate from being impregnated with the varnish.

[0038] [Comparative Example 2] In Comparative Example 2, the first mixing step S2 and the second mixing step S3 of the prepreg manufacturing method shown in Figure 1 were combined into a single solvent mixing step, using only methyl cellosolve as the solvent. Specifically, 100 parts (e.g., 780 g) of methyl cellosolve were weighed and added to the PEG-lignin derivative weighed in step S1, and the mixture was stirred in a mixer for 2 minutes. In this case, at the completion of the mixing steps up to step S4, the varnish (matrix resin raw material composition) was completely transparent, confirming a uniform mixture in which the main component and the curing agent were sufficiently miscible. However, when the cross-section of the fiber-reinforced resin was observed after the completion of the press molding step S9, voids were found inside, confirming that the solvent did not completely evaporate in the drying step S7 and remained.

[0039] [Comparative Example 3] In Comparative Example 3, the first mixing step S2 and the second mixing step S3 of the prepreg manufacturing method shown in Figure 1 were combined into a single solvent mixing step, using methyl ethyl ketone (MEK) (CH3COC2H5) (SP value: 9.3 [cal / cm³]). 3 ] 1 / 2Only (boiling point: 79°C) was used as a solvent. Specifically, 100 parts (e.g., 780 g) of MEK was weighed and added to the PEG-lignin derivative weighed in step S1, and stirred in a mixer for 2 minutes. In this case, the PEG-lignin derivative could not be sufficiently dissolved, and a uniformly mixed varnish (matrix resin raw material composition) could not be obtained.

[0040] [Comparative Example 4] In Comparative Example 3, the first mixing step S2 and the second mixing step S3 of the prepreg manufacturing method shown in Figure 1 were combined into a single solvent mixing step, using only ethyl alcohol (ethanol) (C2H5OH) (boiling point: 78°C) as the solvent. Specifically, 100 parts (e.g., 780 g) of ethanol were weighed and added to the PEG-lignin derivative weighed in step S1, and the mixture was stirred in a mixer for 2 minutes. In this case as well, the PEG-lignin derivative could not be sufficiently dissolved, and a uniformly mixed varnish (matrix resin raw material composition) could not be obtained.

Claims

1. An impregnation step in which a matrix resin raw material composition containing the main component of the matrix resin, a curing agent, and a solvent is impregnated into a fibrous substrate, A method for producing a prepreg, comprising a drying step of drying the matrix resin raw material composition impregnated into the fiber substrate in the impregnation step, The main component is an epoxy resin. The curing agent is a PEG lignin derivative, The aforementioned solvent is A first solvent consisting of glycol ethers, A method for producing a prepreg, characterized by comprising a second solvent consisting of ethers.

2. In the prepreg manufacturing method described in claim 1, The boiling point of the first solvent is 120°C or higher and 140°C or lower. A method for producing a prepreg, characterized in that the boiling point of the second solvent is 25°C or higher and 110°C or lower.

3. In the prepreg manufacturing method according to claim 1 or 2, The process further includes a mixing step of mixing the main component, the curing agent, and the solvent to obtain the matrix resin raw material composition, The aforementioned mixing step is A first mixing step of mixing the curing agent and the first solvent, A method for producing a prepreg, comprising a second mixing step of mixing a mixed composition of the curing agent and the first solvent with the second solvent.

4. In the prepreg manufacturing method according to claim 1 or 2, A method for producing a prepreg, characterized in that the main component is at least one of epoxidized soybean oil and sorbitol glycidyl ether.

5. In the prepreg manufacturing method according to claim 1 or 2, The first solvent is methyl cellosolve, A method for producing a prepreg, characterized in that the second solvent is tetrahydrofuran.

6. A matrix resin raw material composition comprising a main component, a curing agent, and a solvent, The main component is an epoxy resin. The curing agent is a PEG lignin derivative, The aforementioned solvent is A first solvent consisting of glycol ethers, A matrix resin raw material composition characterized by comprising a second solvent consisting of ethers.

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