Solvent-based adhesive composition and joint structure

Abstract

To provide a solvent-based adhesive composition which is suitable for joining a resin pipe and a transparent resin joint and can suppress color unevenness of a joint part, and a joint structure joined by the solvent-based adhesive composition.SOLUTION: A solvent-based adhesive composition contains a resin, an organic solvent and a coloring agent, wherein the coloring agent contains both a pigment and a dye. A joint structure is obtained by joining a resin pipe and a transparent resin joint by the solvent-based adhesive composition.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a solvent-based adhesive composition used for connecting a resin pipe and a resin joint, and a joint structure joined by the solvent-based adhesive composition. More specifically, the present invention relates to a solvent-based adhesive composition suitable for joining a resin pipe and a transparent resin joint, and a joint structure thereof.

Background Art

[0002] A solvent-based adhesive composition (hereinafter simply referred to as "adhesive") is used for joining a resin pipe such as a vinyl chloride pipe and a resin joint such as a vinyl chloride joint. Generally, the adhesive is applied to the outer surface of the pipe end and the inner surface of the receiving port of the joint, and the pipe is inserted into the receiving port to perform the joining.

[0003] Whether or not the adhesive is applied to the pipe and the joint can be confirmed by visually checking whether the adhesive protrudes from the edge of the joint. If there is an overhang of the adhesive, it can be determined that the adhesive has been applied, and if there is no overhang, it can be determined that the adhesive has not been applied. In order to enhance the visibility of the adhesive, the adhesive is not transparent but is colored by adding a colorant.

[0004] A dye is used as the colorant. However, during the joining operation, if the adhesive spills onto the floor surface, when a floor covering such as a floor sheet is laid on top of it, the dye will permeate through the floor covering and seep out to the surface over time. This seepage occurs because the dye is a colorant that is soluble in organic solvents.

[0005] Therefore, in Patent Document 1, a pigment that is insoluble in organic solvents and has a particle size is used as the colorant. As a result, even if a floor covering such as a floor sheet is laid on the floor surface where the adhesive has spilled, the particulate pigment will not permeate through the floor sheet, so seepage can be prevented.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In recent years, transparent resin joints such as transparent vinyl chloride joints have become popular as joints. A transparent joint is suitable not only for visually checking the application state of an adhesive but also for visually checking whether a pipe is inserted to the correct position of the joint.

[0008] Since the clearance between the outer diameter of a pipe and the inner diameter of a transparent joint is small, when an adhesive containing a pigment is used for joining the pipe and the transparent joint, the pigment may be extruded only to the joint end side because of its large particle size. Of course, since the resin component of the adhesive reaches the inside of the joint, there is no problem with the joining effect.

[0009] As a result of the pigment being extruded to the joint end side region, the amount of pigment in the pipe end side region on the back side of the joint decreases, and the joint end side region becomes dark-colored and the pipe end side region becomes light-colored, resulting in color unevenness at the joint. When visually checking whether the adhesive is correctly applied to the joint through the transparent joint, this color unevenness may make it appear that there is uneven coating of the adhesive, and it may not be possible to make a correct judgment.

[0010] An object of the present invention is to provide a solvent-based adhesive composition suitable for joining a resin pipe and a transparent resin joint and capable of suppressing color unevenness at the joint, and a joint structure joined by the solvent-based adhesive composition.

MEANS FOR SOLVING THE PROBLEM

[0011] The solvent-based adhesive composition of the present invention is a solvent-based adhesive composition containing a resin, an organic solvent, and a colorant, wherein the colorant contains both a pigment and a dye.

[0012] It is desirable that the colorant be 0.05% by mass to 4.0% by mass.

[0013] It is desirable that the mass ratio of the pigment to the dye is 90:10 to 40:60.

[0014] It is desirable that the average particle diameter of the pigment is 125 nm to 250 nm.

[0015] The solvent-based adhesive composition is used for joining the tube and the transparent joint, and the cured solvent-based adhesive composition has an L by the diffuse light reflection SCE method in the tube end-side region where the edge of the tube is located with respect to the joint end-side region on the edge side of the joint. * a * b * It is desirable that the color difference ΔE in the color space is 5.0 or less.

[0016] The solvent-based adhesive composition is used for joining the tube and the transparent joint, and the cured solvent-based adhesive composition has an L by the total light reflection SCI method in the tube end-side region where the edge of the tube is located with respect to the joint end-side region on the edge side of the joint. * a * b * It is desirable that the color difference ΔE in the color space is 5.0 or less.

[0017] The solvent-based adhesive composition is used for joining the tube and the transparent joint, and the cured solvent-based adhesive composition has an L by the diffuse light reflection SCE method or the total light reflection SCI method in the tube end-side region where the edge of the tube is located with respect to the joint end-side region on the edge side of the joint. * a * b * The difference Δa * or Δb * is preferably 3.5 or less.

[0018] Moreover, the joint structure of the present invention is formed by joining a resin tube and a transparent resin joint with the above-described solvent-based adhesive composition.

Advantages of the Invention

[0019] The solvent-based adhesive composition of the present invention contains a pigment and a dye as colorants. When a pipe and a fitting are joined, the pigment, which has particle size, moves to the fitting end region due to the clearance between the pipe and the fitting and develops color. On the other hand, the dye, which is dissolved in the organic solvent, remains in the pipe end region and develops color there. Therefore, a fitting structure formed by joining a pipe and a fitting with the solvent-based adhesive composition of the present invention can suppress color unevenness between the fitting end region and the pipe end region. Consequently, when a transparent resin fitting is used as the fitting, it becomes easy to visually confirm whether the adhesive has been properly applied to the joint by looking through the transparent fitting.

[0020] Furthermore, since the solvent-based adhesive composition of the present invention contains both a pigment and a dye as a coloring agent, the amount of dye can be reduced compared to the case where a dye alone is used. Because the amount of dye is reduced, even if the adhesive spills onto the floor, the dye can be suppressed over time from seeping into the flooring material, such as a floor sheet, laid on top of it. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 is a perspective view showing a resin pipe and a transparent resin fitting. [Figure 2] Figure 2 is a perspective view showing a joint structure in which a resin pipe and a transparent resin joint are joined using a solvent-based adhesive composition. [Figure 3] Figure 3 shows photographs of Invention Examples 2-5 and Comparative Example 7 after the adhesive has cured. [Modes for carrying out the invention]

[0022] An embodiment of the solvent-based adhesive composition of the present invention will be described below.

[0023] The solvent-based adhesive composition of the present invention is a composition comprising a resin, an organic solvent, and a colorant, wherein the colorant includes both pigments and dyes.

[0024] <Resin> The resin contained in the solvent-based adhesive composition of the present invention is a resin soluble in organic solvents. Examples of resins include vinyl resins such as polyvinyl chloride resin, chlorinated polyvinyl chloride resin, and acrylic resin. The resin is not limited to one type; multiple types may be used.

[0025] To ensure the bonding strength of the adhesive, the resin is preferably included in the solvent-based adhesive composition at a concentration of 5.0% by mass or more, and more preferably at a concentration of 10% by mass or more. The upper limit of the resin is preferably 30% by mass or less, and more preferably 20% by mass or less.

[0026] <Solvent> The organic solvent contained in the solvent-based adhesive composition of the present invention is a solvent that is soluble in resin. Examples of organic solvents include, but are not limited to, alcohol-based organic solvents, ester-based organic solvents, ketone-based organic solvents, aliphatic hydrocarbon-based organic solvents, ether-based organic solvents, chlorine-based organic solvents, aromatic hydrocarbon-based organic solvents, amide-based organic solvents, and glycol ether-based organic solvents. The organic solvent is not limited to one type, but may also be a mixed organic solvent obtained by mixing multiple types.

[0027] The solvent is preferably included in the solvent-based adhesive composition at a concentration of 70% by mass or more, and more preferably at a concentration of 80% by mass or more, in order to adjust the viscosity of the adhesive, improve its applicability, and facilitate insertion of the pipe into the fitting socket. The upper limit of the solvent is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0028] <Coloring agent> The colorants contained in the solvent-based adhesive composition of the present invention include both pigments and dyes. In the present invention, pigments refer to colorants that are insoluble in organic solvents, and dyes refer to colorants that are soluble in organic solvents.

[0029] -Pigment- Both inorganic and organic pigments can be used.

[0030] Examples of inorganic pigments include natural pigments such as yellow ochre, chromates such as lead yellow, zinc yellow, and barium yellow, ferrocyanides such as Prussian blue, oxides such as titanium white, iron oxide, zinc oxide, and iron black, sulfides such as cadmium yellow and cadmium red, sulfates such as barium sulfate, silicates such as calcium silicate and ultramarine, metal powders such as bronze powder and aluminum powder, and chrome green.

[0031] Examples of organic pigments include natural dye lakes such as mada lake, nitroso pigments such as naphthol green, azo pigments such as carmine 6B, watchang red, pyralozone red, benzidine yellow, and hansa yellow, basic dye lakes such as rhodamine lake and malachite green lake, mordant dyes such as alizarin lake, vat dyes such as indanthrene blue and indigo blue, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, fluorescent pigments, and azine pigments.

[0032] The lower limit of the average particle diameter of the pigment is preferably 125 nm or more, more preferably 140 nm or more, and desirablely 150 nm or more. The upper limit is preferably 250 nm or less, more preferably 190 nm or less, and desirablely 170 nm or less. If the average particle diameter of the pigment is too small, the dispersibility in the solvent deteriorates, the pigment is more likely to aggregate, and color unevenness is more likely to occur. If the average particle diameter is too large, the storage stability deteriorates, the pigment precipitates, and the color tone becomes disordered. Therefore, the above numerical ranges are preferable. The average particle diameter is defined as the volume average particle diameter (D) as shown in the Japanese Industrial Standard (JIS Z8901) as the "equivalent spherical diameter by light scattering method". 50 )

[0033] To prevent the pigment from settling or separating in the solvent, the lower limit of the specific gravity of the pigment is preferably 1.3 or higher, more preferably 1.4 or higher, and desirablely 1.6 or higher. The upper limit is preferably 2.0 or lower, more preferably 1.8 or lower, and desirablely 1.7 or lower. Specific gravity should be measured according to JIS Z8807.

[0034] Pigments can be used individually or in combination of multiple types.

[0035] -dye- Both oil-soluble and water-soluble dyes can be used.

[0036] Examples of oil-soluble dyes include monoazo dyes such as Fast Orange R, Oil Red, Oil Yellow (Solvent Yellow 163), and Oil Blue (Solvent Blue 35, Solvent Blue 97); anthraquinone dyes such as anthraquinone blue and anthraquinone violet; azine dyes such as nigrosine and indurine; and other basic dyes, acid dyes, and metal complex compound dyes.

[0037] Examples of water-soluble dyes include basic dyes such as rhodamine B, acidic dyes such as orange II, and fluorescent dyes.

[0038] The content of colorants, including pigments and dyes, in the solvent-based adhesive composition is not particularly limited, but in order to ensure visibility, the lower limit is 0.05% by mass or more, preferably 0.1% by mass, and most likely 0.15% by mass of the solvent-based adhesive composition, and the upper limit is 4.0% by mass or less, preferably 2.0% by mass or less, and most likely 1.0% by mass or less.

[0039] In the solvent-based adhesive composition of 1, it is preferable to use pigments and dyes of the same color family. For example, if phthalocyanine blue, a blue pigment, is used, then solvent blue 35, a blue dye, should also be used. This is because if pigments and dyes of different color families are used, color unevenness will occur as the dye will disperse evenly at the joint while the pigment moves to the joint end area.

[0040] While there are no particular limitations on the mass ratio of pigment to dye in the coloring agent, too much pigment can lead to uneven coloring (color difference) at the joints, and too much dye can cause bleeding onto the floor sheet. For this reason, a mass ratio of 90:10 to 40:60 for pigment to dye is preferable, 80:20 to 50:50 is preferable, and 70:30 to 60:40 is more desirable.

[0041] Furthermore, when a resin pipe and a transparent resin fitting are joined using a solvent-based adhesive composition containing pigments and dyes of the same hue, and the adhesive hardens, in order to suppress color unevenness at the joint, the joint is subjected to a diffuse light reflection SCE method for the pipe end side region where the pipe edge is located relative to the joint end side region on the end edge side of the fitting. * a * b * It is preferable to have a color difference ΔE of 5.0 or less in the color space, and it is desirable to have a color difference ΔE of 3.0 or less. If the color difference ΔE is 5.0 or less, the viewer can perceive the colors as almost identical even when comparing them over time, making it easier to judge color unevenness at the joint.

[0042] In this invention, the joint end region and the pipe end region are defined as follows: As shown in Figure 2, in a joint 40 where the pipe 20 and the joint 30 are joined with adhesive, the joint end region, as indicated by reference numeral 41, means the region within 40% of the joint length from the front end surface of the joint 30 toward the back. The pipe end region, as indicated by reference numeral 42, means the region within 40% of the joint length from the front end surface of the pipe 20 inside the joint 30 toward the front (joint end region 41).

[0043] Furthermore, when a resin pipe and a transparent resin fitting are joined using a solvent-based adhesive composition containing pigments and dyes of the same hue, and the adhesive hardens, in order to suppress color unevenness at the joint, the joint is subjected to a total light reflection SCI method for the pipe end side region where the pipe edge is located relative to the joint end side region on the end edge side of the fitting. * a * b *It is preferable to have a color difference ΔE of 5.0 or less in the color space, and it is desirable to have a color difference ΔE of 3.0 or less. If the color difference ΔE is 5.0 or less, the viewer can perceive the colors as almost identical even when comparing them over time, making it easier to judge color unevenness at the joint.

[0044] In addition, instead of the above, L * a * b * Coordinate a in the diffuse ray reflection SCE method or total ray reflection SCI method of color space * or b * The difference Δa * or Δb * It is preferable to set it to 3.5 or less, and it is desirable to set it to 3.0 or less. Depending on the hue of the pigment and dye, Δa * or Δb * One of them can be measured, and the other can be omitted. That is, if the pigment and dye are red or green, Δa * Measure the value, and if the pigment and dye are blue or yellow, then Δb * You should measure this. The other will be a small value. And the color difference Δa * or Δb * If the value is 3.5 or less, the viewer can perceive the colors as nearly identical even when comparing them over time, making it easier to judge color unevenness at the joint.

[0045] <Other> The solvent-based adhesive composition of the present invention may contain stabilizers and thickeners in addition to the above-mentioned components. Examples of stabilizers include lead-based stabilizers, organotin-based stabilizers, and cadmium-based stabilizers. Examples of thickeners include inorganic silicates, organic bentonite, inorganic bentonite, fatty acid bisamide, and hydrogenated castor oil.

[0046] <Solvent-based adhesive composition> A solvent-based adhesive composition is prepared by measuring and mixing the above-mentioned resin, organic solvent, colorant consisting of pigments and dyes, and, if necessary, stabilizers and thickeners.

[0047] <Resin pipes and resin fittings to be joined> The resin pipe and resin fitting are joined using the above solvent-based adhesive composition. The resin pipe and resin fitting are made from resins that are soluble in the organic solvent contained in the adhesive, at least one, and more preferably both. Examples of such resins include vinyl chloride resins and (meth)acrylic resins, which may be used alone or in combination of two or more. Examples of vinyl chloride resins include vinyl chloride homopolymers; vinyl chloride monomers; copolymers of vinyl chloride monomers and polymerizable monomers having unsaturated bonds copolymerizable with vinyl chloride monomers; and graft copolymers obtained by graft copolymerizing a polymer with vinyl chloride monomers. These may be used alone or in combination of two or more.

[0048] The solvent-based adhesive composition of the present invention has the effect of suppressing color unevenness in the joint between a pipe and a fitting, from the joint end area to the pipe end area. To effectively achieve this effect, it is desirable that the fitting covering the outside of the joint be made of a transparent resin, such as transparent polyvinyl chloride, so that the joint can be seen. The pipe may be a commonly used gray color. Of course, the pipe may also be made from a transparent resin.

[0049] <Joint structure> A resin pipe and a resin fitting, preferably a transparent resin fitting, are joined using the solvent-based adhesive composition of the present invention. The adhesive is evenly applied to the outer surface of the pipe and the inner surface of the fitting's socket, and the pipe is inserted into the socket and allowed to dry. This completes the joining of the pipe and the fitting, and a fitting structure is obtained. It is preferable to apply an amount of adhesive such that it overflows from the end of the fitting when the pipe is inserted into the socket.

[0050] The solvent-based adhesive composition of the present invention contains both a pigment and a dye as a coloring agent. Therefore, when a pipe is inserted into the socket of a fitting, even if the pigment in the pipe end area moves to the fitting end area due to the clearance between the pipe and the fitting, the dye remains in the pipe end area, thus suppressing the occurrence of color unevenness. Consequently, in the fitting structure of the present invention, it is easy to visually confirm whether the adhesive has been properly applied to the joint.

[0051] Furthermore, since the coloring agent contains both pigments and dyes, the amount of dye can be reduced compared to when dyes are included alone in the solvent-based adhesive composition. By reducing the amount of dye contained in the solvent-based adhesive composition, even if adhesive spills onto the floor and flooring materials such as floor sheets are laid on top, the bleeding of dye over time can be suppressed. [Examples]

[0052] Solvent-based adhesive compositions of the inventive example and comparative example were prepared with the compositions shown in Table 1. The colorants are indicated by the mass ratio of pigments and dyes.

[0053] [Table 1]

[0054] The PVC resin used in the solvent-based adhesive composition is a polyvinyl chloride homopolymer with an average degree of polymerization of 800. The organic solvent is a mixture of organic solvents with a boiling point of 50-150°C (cyclohexanone:methyl ethyl ketone:acetone = 45:30:20 (mass ratio)). Phthalocyanine blue (blue organic pigment) was added as a colorant, and Solvent Blue 35 (blue) was added as a dye in the weight ratios shown in Table 1. The average particle size of phthalocyanine blue is 50 nm. The colorant was added to a concentration of 0.4% by mass of the prepared solvent-based adhesive composition.

[0055] Table 1 lists the inventive examples and comparative examples in descending order of pigment mass ratio. Specifically, Comparative Example 1 is an example using only pigment, Inventive Examples 2 to 6 are examples with pigment:dye ratios of 80:20 to 40:60, and Comparative Example 7 is an example using only dye.

[0056] The solvent-based adhesive compositions of the above-mentioned example invention and comparative example were subjected to the following evaluation tests.

[0057] <Storage stability> The storage stability of the solvent-based adhesive compositions in each example was evaluated. For storage stability, 100g of the solvent-based adhesive composition was placed in a UM sample bottle (model number 5-128-03), sealed, and stored at 40°C for 2 months. As a result, no precipitation or separation of the colorant was observed in any of the examples (evaluation: ○).

[0058] <PVC sheet bleed-through properties> Test specimens were obtained by applying 1 g of the solvent-based adhesive composition of each example to the back surface of a flexible polyvinyl chloride sheet (manufactured by Toli Corporation, model number TS2118, thickness 2.0 mm) and drying it. The test specimens were left to stand for 24 to 120 hours under normal pressure and 60°C, and the presence or absence of color changes on the surface and cross-section of the sheet was visually evaluated every 24 hours. The results are shown in Table 2. In Table 2, "○" indicates that there was no color change on the surface or cross-section of the sheet, "△" indicates that no color change was visible on the surface of the sheet but color diffusion was observed in the cross-section, and "×" indicates that a color change (bleed-out) was visible on the surface of the sheet.

[0059] [Table 2]

[0060] Referring to Table 2, Comparative Example 1, which used only pigment, showed no color change on the sheet surface or cross-section even after 120 hours. For Invention Examples 2-5, there was no color change on the sheet surface or cross-section for 24-48 hours, but color diffusion to the sheet cross-section was observed in the following 24-48 hours, and then color bleeding to the sheet surface was observed thereafter. For Invention Example 6, color diffusion to the sheet cross-section was observed after 24 hours, and then color bleeding to the sheet surface was observed thereafter. On the other hand, for Comparative Example 7, which used only dye, color bleeding to the sheet surface was observed after 24 hours.

[0061] Comparing these examples, it was found that as the proportion of dye in the coloring agent increased, the color bleeding to the sheet surface progressed.

[0062] Based on the results in Table 2, the PVC sheet bleed-through properties of the examples were evaluated on a four-point scale. The evaluation criteria were as follows: "◎" was used for examples where there was no color change on the surface and cross-section of the sheet after 48 hours (all examples marked "○"). Additionally, "○" was used for examples where there was no color change on the surface and cross-section of the sheet after 24 hours (examples marked "○" at 24 hours), "△" was used for examples where there was color diffusion to the cross-section of the sheet after 24 hours (examples marked "△" at 24 hours), and "×" was used for examples where color bleed-through to the sheet surface after 24 hours (examples marked "×" at 24 hours). The results are shown in Tables 1 and 2 above.

[0063] Referring to Tables 1 and 2, Comparative Example 1, Invention Examples 2 and 3 received an evaluation of "◎", Invention Examples 3-5 received an evaluation of "○", Invention Example 6 received an evaluation of "△", and Comparative Example 7 received an evaluation of "×". Regarding the bleedability of the PVC sheet, it can be seen that better results are obtained with less dye.

[0064] <Visibility> Using the solvent-based adhesive composition of each embodiment, a rigid polyvinyl chloride resin pipe 20 (VP) shown in Figure 1 and a rigid polyvinyl chloride transparent joint 30 (transparent DS) for drainage were joined to create a joint structure 10. The joint 40 was visually inspected through the joint 30, and the color difference ΔE of the pipe end side region 42 where the edge of the pipe 20 is located was measured with respect to the joint end side region 41 on the edge side of the joint 30 shown in Figure 2.

[0065] The adhesive was applied to the inner surface of the socket 31 of the joint 30 shown in Figure 1, and the pipe 20 was inserted into the socket 31 as shown in Figure 2, and then allowed to harden.

[0066] Figure 3 shows photographs of Invention Examples 2-5 and Comparative Example 7 after the adhesive has cured. Referring to Figure 3, in Comparative Example 7, almost no color unevenness was observed in the joint 40. Similarly, in Invention Examples 2-5, almost no color unevenness was observed by visual inspection.

[0067] For Invention Examples 2-6, using the CM-2500c manufactured by Konica Minolta, Inc., the L of the joint end region 41 and the pipe end region 42 * a * b *L in color space * a * b * The values ​​were measured using the diffuse light reflection SCE method and the total light reflection SCI method, and the color difference between the two was ΔE (=√(ΔL)). * ) 2 +(Δa * ) 2 +(Δb * ) 2 ) was calculated.

[0068] Note that the L of the pipe * a * b * The value is brightness L * Value: 43, chromaticity a * Value: -2, chromaticity b * The value was -2.

[0069] Generally, if the color difference ΔE of both SCE and SCI is 5 or less, viewers can perceive them as nearly identical colors even when comparing them over time. On the other hand, if the color difference ΔE exceeds 5.0, viewers can distinguish them to some extent (Color Science Association, Handbook of Colored Paper Science). Therefore, the threshold for judging color unevenness at the joint 40 was set to a color difference ΔE = 5.0.

[0070] The results are shown in Table 3. Referring to Table 3, the color difference ΔE of both SCE and SCI in Invention Examples 2-6 and Comparative Example 7 was 5.0 or less (evaluation "○"). This is because the proportion of dye in the colorant increased and the proportion of pigment with particle size decreased, resulting in the dye remaining evenly in the joint 40, and the amount of pigment extruded into the joint end region 41 decreased. On the other hand, in Comparative Example 1, which contained only pigment, the color difference ΔE of both SCE and SCI exceeded 8.0, and the color unevenness was easily discernible even by visual inspection (evaluation "×"). This is because the pigment was extruded into the joint end region 41, while it did not contain dye that remains in the pipe end region 42 and suppresses color unevenness, as in the other examples.

[0071] [Table 3]

[0072] Furthermore, since the pigments and dyes used in this embodiment are all blue, for each embodiment, the b of the joint end region 41 and the pipe end region 42 was determined by the total light reflection SCI method. * Measure the value and the difference Δb * The result was calculated and is shown in Table 4.

[0073] [Table 4]

[0074] Difference Δb * If the difference is 3.5 or less, the viewer can perceive the color as almost identical even when comparing it over time. On the other hand, the difference Δb * When the difference exceeds 3.5, it becomes possible for the viewer to distinguish the difference to some extent (Color Science Association, Color Paper Science Handbook). Therefore, the threshold that serves as the criterion for judging the color unevenness of the joint 40 is set to the difference Δb. * I set it to =3.5.

[0075] Referring to Table 4, Examples 2-6 and Comparative Example 7 have a joint end region 41 and a pipe end region b * Difference in value Δb * All of these values ​​were 3.5 or less (evaluation "○"). This is because, similar to the color difference ΔE, the proportion of dye in the colorant increased and the proportion of pigment with particle size decreased, resulting in the dye remaining evenly in the joint 40 and the amount of pigment pushed out to the joint end region 41 decreased. On the other hand, in comparative example 1, which used only pigment, b * Difference in value Δb * The value was above 3.5 (rating "×"). This is because the pigment was pushed out to the joint end region 41, while it remained in the pipe end region 42 as in other embodiments and does not contain the dye that suppresses color unevenness.

[0076] As described above, in this embodiment, blue is used for the pigment and dye, so the color difference ΔE and b due to SCE and SCI are * Difference Δb by value * All results were the same. These results are shown together in Table 1 under "Visibility".

[0077] Also, if the pigment and dye are yellow, then b * Difference Δb by value * 3.5 below It is desirable that the pigment and dye be red or green, a * Difference Δa by value * 3.5 below This is desirable.

[0078] <Adhesion Evaluation> The adhesive strength (MPa) of the joined pipe 20 and transparent fitting 30 was measured after 15 minutes and 2 hours, according to the JWWA S101-2006 standard for adhesives for rigid polyvinyl chloride water pipes. According to this standard, an adhesive strength of 1.25 MPa or higher after 15 minutes and 2.5 MPa or higher after 2 hours was considered acceptable.

[0079] The measurement results showed that all examples met the above adhesive strength requirements. Therefore, the result was evaluated as "○" as shown in Table 1.

[0080] <Summary> Referring to the results of the evaluation tests described above, Invention Examples 2-6, which contain both pigments and dyes as colorants, are superior to Comparative Example 7, which uses only dyes, in terms of PVC sheet bleed-through. Furthermore, Invention Examples 2-6 are superior to Comparative Example 1, which uses only pigments, in terms of visibility.

[0081] Furthermore, comparing the examples of inventions reveals that the higher the proportion of pigment, the better the PVC sheet's ability to bleed through, and the higher the proportion of dye, the better the visibility. To achieve both of these properties, it is preferable that the mass ratio of pigment to dye be between 80:20 and 50:50.

[0082] The above description of the embodiments is for the purpose of explaining the present invention and should not be interpreted as limiting or narrowing the scope of the invention described in the claims. Furthermore, the configuration of each part of the present invention is not limited to the above embodiments, and various modifications are possible within the technical scope described in the claims. [Explanation of Symbols]

[0083] 10 Joint Structure 20 Resin pipes 30 Transparent fittings 31 socket 40 Joint 41 Joint end area 42 Pipe end area

Claims

1. A solvent-based adhesive composition for joining synthetic resin pipes and transparent resin fittings, Contains resin, organic solvent and colorant, The aforementioned coloring agent contains both a pigment and a dye of the same color family. When the resin pipe and the transparent resin joint are joined and hardened, the pipe end region where the edge of the resin pipe is located relative to the joint end region on the edge side of the joint, (1) The color difference ΔE in the L * a * b * color space using the diffuse light reflection SCE method is 5.0 or less. (2) The color difference ΔE in the L*a*b* color space using the total light reflection SCI method is 5.0 or less, and (3) The difference Δb* in the L*a*b* color space using the diffuse light reflection SCE method or the total light reflection SCI method is 3.5 or less. Solvent-based adhesive composition.

2. The coloring agent comprises a blue-colored pigment and a blue-colored dye. The solvent-based adhesive composition according to claim 1.

3. The pigment is a phthalocyanine blue pigment, and the dye is a solvent blue dye. The solvent-based adhesive composition according to claim 2.

4. The coloring agent is present in an amount of 0.05% to 4.0% by mass. The solvent-based adhesive composition according to claim 1.

5. The ratio of the pigment to the dye is 90:10 to 40:60 by mass. The solvent-based adhesive composition according to claim 1.

6. A resin pipe and a transparent resin fitting are joined together using a solvent-based adhesive composition according to any one of claims 1 to 5. Joint structure.

Images