A production process of tinned copper wire for avoiding shedding of the tin coating

Abstract

The present invention relates to a production process of tinned copper wire for avoiding the shedding of the tin coating, which comprises the following steps: Step 1, material preparation: Select copper wire made of pure copper and perform annealing treatment in a high-temperature furnace; Step 2, pretreatment: Immerse the annealed copper wire in a soldering flux and then place it in an oven for drying to obtain the pretreated copper wire; Step 3, tin plating: Place the pretreated copper wire in a tin plating furnace for tin plating treatment to obtain the pretreated tinned copper wire; Step 4, post-treatment: Place the pretreated tinned copper wire in water again to wash away impurities, and after vacuum drying, obtain the tinned copper wire. In this process, annealing treatment is first performed on the copper wire to make the copper wire soft and eliminate internal residual stress. Before tin plating, the copper wire is treated with a soldering flux and then subjected to high-temperature tin plating treatment. Such operations can increase the adhesion of the tin coating, largely avoid the subsequent shedding of the tin coating, and improve the use effect and service life of the product.

Description

Technical Field

[0001] The present invention relates to the field, and particularly relates to a production process of tinned copper wire for avoiding the shedding of the tin coating. Background Art

[0002] Copper is widely used in industry and daily life due to its excellent electrical conductivity, thermal conductivity and chemical stability. Tinned copper wire refers to a copper wire with a thin layer of metallic tin plated on its surface. Tinned copper wire is relatively soft in texture and has good electrical conductivity. Compared with bare copper wire, it has stronger corrosion resistance and antioxidant properties, and can greatly extend the service life of weak electric wires and cables. Tin plating on copper conductors can prevent the insulating rubber from becoming sticky, the wire core from turning black and brittle, and improve its solderability. Tinned copper wire is mainly used as a conducting wire core for mining cables, flexible wires, flexible cables and marine cables with rubber insulation, as well as for the outer braided layer of cables and brush wires.

[0003] Tinned copper wire has a variety of excellent properties, and its processing technology is simple, but the process flow is relatively many. At present, in the production of tinned copper wire in China's wire and cable industry, there are mainly two methods: chemical tin plating and physical tin plating. During the process of physical tin plating, there is a very thin oxide layer on the surface of the copper wire after annealing. Direct tin plating will cause problems such as uneven tin plating, frequent wire breakage of the copper wire during tin plating, and copper leakage of the tinned copper wire. Therefore, before entering the tin furnace, it must be cleaned with an appropriate pickling solution (flux) to ensure good adhesion between the tin layer and the copper wire. It can be said that pickling directly affects the tin plating effect and product performance of tinned copper wire, and is one of the important links in the production of tinned copper wire. If not controlled properly, it will cause poor adhesion of the tin coating on the surface, easy shedding, etc., affecting the use effect and service life of the product, and thus affecting the production quality of tinned copper wire. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a production process of tinned copper wire for avoiding the shedding of the tin coating.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A production process of tinned copper wire for avoiding the shedding of the tin coating, comprising the following steps:

[0007] Step 1, Material Preparation:

[0008] Select copper wire made of pure copper material and perform annealing treatment in a high-temperature furnace;

[0009] Step 2, Pretreatment:

[0010] Immerse the annealed copper wire in the flux, and then place it in an oven for drying to obtain the pretreated copper wire;

[0011] Step 3, Tin Plating:

[0012] Place the pretreated copper wire in a tin plating furnace for tin plating treatment to obtain pretreated tinned copper wire.

[0013] Step 4. Post-treatment:

[0014] Place the pretreated tinned copper wire in water again to wash away impurities, and after vacuum drying, obtain tinned copper wire.

[0015] Preferably, in the step 1, the purity of the copper wire is ≥99.99%, and the diameter is 0.15 - 0.25 mm.

[0016] Preferably, in the step 1, the temperature of the annealing treatment is 650 - 720 °C, and the time is 1 - 2 h.

[0017] Preferably, in the step 2, during the process of immersing the annealed copper wire in the soldering flux, the surface of the copper wire is completely coated with the soldering flux.

[0018] Preferably, in the step 2, the temperature in the oven is 80 - 90 °C, and the drying time is 1 - 2 h.

[0019] Preferably, in the step 3, the temperature in the tin plating furnace is 230 - 250 °C, and the residence time is 2 - 5 s.

[0020] Preferably, the components of the soldering flux in the step 2 are calculated by weight and include:

[0021] 40 - 60 parts of modified rosin resin, 16 - 20 parts of lubricant, 12 - 18 parts of metal chloride, 3 - 8 parts of dispersant, and 10 - 20 parts of solvent.

[0022] Preferably, the metal chloride is one or a combination of zinc chloride, magnesium chloride, samarium chloride, and sodium chloride.

[0023] Preferably, the lubricant is hexadecanoic acid or octadecanoic acid.

[0024] Preferably, the dispersant is ethylene glycol monobutyl ether or propylene glycol monobutyl ether.

[0025] Preferably, the solvent is one of isopropyl alcohol, toluene, and ethyl acetate.

[0026] Preferably, the preparation method of the modified rosin resin includes:

[0027] S1. Weigh hydrogenated rosin resin and epoxy resin and mix them, add a catalyst, heat up to 80 - 100 °C under the protection of nitrogen, stir and react for 3 - 6 h, then add acrylic monomer, continue to react for 2 - 5 h, after the reaction ends, cool down to room temperature to obtain acrylic rosin resin;

[0028] S2. Mix acrylic rosin resin and absolute ethanol, then add 2-mercaptobenzimidazole, stir well until homogeneous, then add a photoinitiator, and carry out the reaction under ultraviolet light irradiation at room temperature, stir and react for 2-4 h. After the reaction, remove ethanol under reduced pressure to obtain the modified rosin resin.

[0029] Preferably, in the step S1, the acid value of the hydrogenated rosin resin is 10 mgKOH / g, and the softening point is 86 °C.

[0030] Preferably, in the step S1, the epoxy value of the epoxy resin is 0.132 eq / 100 g, the softening point is 88 °C, and the density is 1.18 g / cm 3 .

[0031] Preferably, in the step S1, the catalyst is tetramethylammonium hydroxide, and the purity > 98%.

[0032] Preferably, in the step S1, the addition amount of the catalyst is 3%-8% of the mass of the hydrogenated rosin resin.

[0033] Preferably, in the step S1, the mass ratio of the hydrogenated rosin resin, the epoxy resin and the acrylic monomer is 1:3.5-4.2:0.63-0.96.

[0034] Preferably, in the step S2, the mass ratio of the acrylic rosin resin, 2-mercaptobenzimidazole and absolute ethanol is 1:0.31-0.62:4-6.

[0035] Preferably, in the step S2, the photoinitiator is benzoin ethyl ether, and the addition amount is 2%-8% of the mass of the acrylic rosin resin.

[0036] Preferably, in the step S2, the wavelength of the ultraviolet light is 365 nm and the power is 50 W.

[0037] Preferably, the soldering flux is prepared by mixing the raw materials and stirring well.

[0038] The beneficial effects of the present invention are as follows:

[0039] 1. The present invention provides a production process for tinned copper wire. In this process, the copper wire is first annealed, which can make the copper wire soft and eliminate internal residual stress. Before tin plating, the copper wire is treated with a soldering flux, and then subjected to high-temperature tin plating treatment. Such an operation can increase the adhesion of the tin plating layer, largely avoid the subsequent peeling off of the tin plating layer, and improve the use effect and service life of the product.

[0040] 2. In the present invention, the soldering flux used is an improvement based on the traditional rosin-based soldering flux. The soldering flux prepared from traditional rosin resin has weak activity and poor surface treatment ability for copper wires. In the present invention, the rosin resin is modified, so that after being applied to the soldering flux, the activity is enhanced. Not only the surface treatment ability for copper wires is improved, but also the mechanical strength of the tinned copper wires is enhanced.

[0041] 3. The preparation process of the modified rosin resin in the present invention is as follows: First, hydrogenated rosin resin and epoxy resin are combined, and then acrylic acid is added for grafting treatment to obtain acrylic rosin ester. Then, using the double bond group in the acrylic acid structure and the mercapto group in 2-mercaptobenzimidazole, a thiol-ene click chemical reaction occurs to introduce the benzimidazole group, thus obtaining the modified rosin resin. Compared with the traditional rosin resin, the modified rosin resin prepared in the present invention has better cross-linking adhesiveness, which can make the solder paste better adhere to the copper wire, thereby achieving a good tin plating effect.

[0042] 4. In addition, through detection, it is found that the copper wires treated with the soldering flux of the present invention have better mechanical strength performance after tin plating. Specific Embodiments

[0043] The technical solutions of the present invention are illustrated by specific specific examples below. It should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combined steps or that other method steps can be inserted between these clearly mentioned steps; it should also be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Moreover, unless otherwise specified, the numbers of the method steps are only convenient tools for identifying the method steps, rather than limiting the arrangement order of the method steps or the scope in which the present invention can be implemented. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0044] To better understand the above technical solutions, the exemplary embodiments of the present invention are described in more detail below. Although the exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0045] The present invention is further described below in conjunction with the following embodiments.

[0046] Embodiment 1

[0047] A production process of tinned copper wire for avoiding tin plating layer peeling off, comprising the following steps:

[0048] Step 1. Material preparation:

[0049] Select copper wire made of pure copper with a purity of the copper wire ≥ 99.99% and a diameter of 0.2 mm, and perform annealing treatment in a high-temperature furnace. The annealing temperature is 680 °C and the time is 2 h;

[0050] Step 2. Pretreatment:

[0051] Immerse the annealed copper wire in the flux so that the surface of the copper wire is completely coated with the flux, and then place it in an oven for drying. The temperature in the oven is 85 °C and the drying time is 1.5 h, thus obtaining the pretreated copper wire;

[0052] Step 3. Tin plating:

[0053] Place the pretreated copper wire in a tin plating furnace. The temperature in the tin plating furnace is 240 °C, perform tin plating treatment, and the residence time is 3.5 s, thus obtaining the pretreated tin-plated copper wire;

[0054] Step 4. Post-treatment:

[0055] Place the pretreated tin-plated copper wire in water again to wash away impurities, and after vacuum drying, obtain the tin-plated copper wire.

[0056] The components of the above flux are calculated by weight and include:

[0057] 50 parts of modified rosin resin, 18 parts of stearic acid, 15 parts of zinc chloride, 5 parts of ethylene glycol monobutyl ether, and 15 parts of isopropanol.

[0058] Among them, the preparation method of the modified rosin resin includes:

[0059] S1. Weigh hydrogenated rosin resin (the acid value of hydrogenated rosin resin is 10 mg KOH / g, and the softening point is 86 °C) and epoxy resin (the epoxy value is 0.132 eq / 100 g, the softening point is 88 °C, and the density is 1.18 g / cm 3 ) and mix them, add the catalyst tetramethylammonium hydroxide (purity > 98%), and the addition amount is 5% of the mass of the hydrogenated rosin resin. Heat up to 90 °C under the protection of nitrogen, stir and react for 5 h, then add acrylic acid (C 3 H 4 O 2 ). The mass ratio of hydrogenated rosin resin, epoxy resin, and acrylic acid monomer is 1:3.8:0.79. Continue to react for 3 h, then end the reaction, and cool down to room temperature to obtain acrylic rosin resin;

[0060] S2. Mix acrylic rosin resin and absolute ethanol, then add 2-mercaptobenzimidazole. The mass ratio of acrylic rosin resin, 2-mercaptobenzimidazole and absolute ethanol is 1:0.46:5. Stir well until homogeneous, then add benzoin ethyl ether as a photoinitiator, and the addition amount is 5% of the mass of acrylic rosin resin. At room temperature, carry out the reaction under the irradiation of ultraviolet light. The wavelength of the ultraviolet light is 365 nm and the power is 50 W. Stir and react for 3 h. After the reaction, remove ethanol under reduced pressure to obtain the modified rosin resin.

[0061] Among them, the preparation of the soldering flux is to mix the raw materials and it can be used after stirring evenly.

[0062] Example 2

[0063] A production process of tinned copper wire to avoid the shedding of the tin plating layer, including the following steps:

[0064] Step 1. Material preparation:

[0065] Select copper wire made of pure copper material, the purity of the copper wire is ≥99.99%, the diameter is 0.15 mm, and carry out annealing treatment in a high-temperature furnace. The temperature of the annealing treatment is 650 °C and the time is 2 h;

[0066] Step 2. Pretreatment:

[0067] Immerse the annealed copper wire in the soldering flux so that the surface of the copper wire is completely coated with the soldering flux, and then place it in an oven for drying. The temperature in the oven is 80 °C and the drying time is 2 h, thus obtaining the pretreated copper wire;

[0068] Step 3. Tin plating:

[0069] Place the pretreated copper wire in a tin plating furnace, the temperature in the tin plating furnace is 230 °C, carry out tin plating treatment, and the residence time is 5 s, thus obtaining the pretreated tinned copper wire;

[0070] Step 4. Post-treatment:

[0071] Place the pretreated tinned copper wire in water again to wash away impurities, and after vacuum drying, obtain the tinned copper wire.

[0072] Above, the components of the soldering flux are calculated by weight and include:

[0073] 40 parts of modified rosin resin, 16 parts of palmitic acid, 12 parts of magnesium chloride, 3 parts of propylene glycol monobutyl ether and 10 parts of toluene.

[0074] Among them, the preparation method of the modified rosin resin includes:

[0075] S1. Weigh hydrogenated rosin resin (the acid value of hydrogenated rosin resin is 10 mg KOH / g, and the softening point is 86 °C) and epoxy resin (the epoxy value is 0.132 eq / 100 g, the softening point is 88 °C, and the density is 1.18 g / cm 3 ) and mix them. Add the catalyst tetramethylammonium hydroxide (purity > 98%), and the addition amount is 3% of the mass of the hydrogenated rosin resin. Heat to 80 °C under the protection of nitrogen, stir and react for 6 h, then add acrylic acid (C 3 H 4 O 2 ). The mass ratio of the hydrogenated rosin resin, epoxy resin and acrylic acid monomer is 1:3.5:0.63. Continue to react for 2 h, then end the reaction and cool down to room temperature to obtain acrylic rosin resin;

[0076] S2. Mix the acrylic rosin resin and absolute ethanol, and then add 2-mercaptobenzimidazole. The mass ratio of the acrylic rosin resin, 2-mercaptobenzimidazole and absolute ethanol is 1:0.31:4. Stir well until homogeneous, then add benzoin ethyl ether as a photoinitiator, and the addition amount is 2% of the mass of the acrylic rosin resin. At room temperature, carry out the reaction under the irradiation of ultraviolet light. The wavelength of the ultraviolet light is 365 nm and the power is 50 W. Stir and react for 2 h. After the reaction ends, remove ethanol under reduced pressure to obtain the modified rosin resin.

[0077] Among them, the preparation of the soldering flux is to mix each raw material and use it after stirring evenly.

[0078] Example 3

[0079] A production process of a tinned copper wire for avoiding the shedding of the tin coating, comprising the following steps:

[0080] Step 1. Material preparation:

[0081] Select a copper wire made of pure copper material, the purity of the copper wire ≥ 99.99%, the diameter is 0.25 mm, and carry out annealing treatment in a high-temperature furnace. The annealing temperature is 720 °C and the time is 1 h;

[0082] Step 2. Pretreatment:

[0083] Immerse the annealed copper wire in the soldering flux so that the surface of the copper wire is completely coated with the soldering flux, and then place it in an oven for drying. The temperature in the oven is 90 °C and the drying time is 1 h, thus obtaining the pretreated copper wire;

[0084] Step 3. Tin plating:

[0085] Place the pretreated copper wire in a tin plating furnace, the temperature in the tin plating furnace is 250 °C, carry out tin plating treatment, and the residence time is 2 s, thus obtaining the pretreated tinned copper wire;

[0086] Step 4. Post-treatment:

[0087] The pre-treated tinned copper wire is placed in clean water again to wash away impurities. After vacuum drying, the tinned copper wire is obtained.

[0088] Above, the components of the soldering flux are calculated by weight and include:

[0089] 60 parts of modified rosin resin, 20 parts of stearic acid, 18 parts of sodium chloride, 8 parts of propylene glycol monobutyl ether, and 20 parts of ethyl acetate.

[0090] Among them, the preparation method of the modified rosin resin includes:

[0091] S1. Weigh hydrogenated rosin resin (the acid value of hydrogenated rosin resin is 10 mg KOH / g, and the softening point is 86 °C) and epoxy resin (the epoxy value is 0.132 eq / 100 g, the softening point is 88 °C, and the density is 1.18 g / cm 3 ) and mix them. Add the catalyst tetramethylammonium hydroxide (purity > 98%). The addition amount is 8% of the mass of the hydrogenated rosin resin. Under the protection of nitrogen, heat up to 100 °C, stir and react for 3 h, then add acrylic acid (C 3 H 4 O 2 ). The mass ratio of hydrogenated rosin resin, epoxy resin, and acrylic acid monomer is 1:4.2:0.96. Continue to react for 5 h, then end the reaction and cool down to room temperature to obtain acrylic rosin resin;

[0092] S2. Mix the acrylic rosin resin and absolute ethanol, and then add 2-mercaptobenzimidazole. The mass ratio of acrylic rosin resin, 2-mercaptobenzimidazole, and absolute ethanol is 1:0.62:6. Stir well until uniform, then add benzoin ethyl ether as a photoinitiator. The addition amount is 8% of the mass of the acrylic rosin resin. At room temperature, carry out the reaction under the irradiation of ultraviolet light. The wavelength of the ultraviolet light is 365 nm, and the power is 50 W. Stir and react for 4 h. After the reaction ends, remove ethanol under reduced pressure to obtain the modified rosin resin.

[0093] Among them, the soldering flux is prepared by mixing the raw materials and can be used after stirring evenly.

[0094] Comparative Example 1

[0095] A production process of tinned copper wire, which is different from Example 1 in that the components of the soldering flux are different, and the modified rosin resin in the components is replaced by hydrogenated rosin resin.

[0096] In this comparative example, the soldering flux includes, calculated by weight:

[0097] 50 parts of hydrogenated rosin resin, 18 parts of stearic acid, 15 parts of zinc chloride, 5 parts of ethylene glycol monobutyl ether, and 15 parts of isopropanol.

[0098] Comparative Example 2

[0099] A production process of tinned copper wire, different from that of Example 1 in that the composition of the soldering flux is different, and the modified rosin resin in the composition is replaced with acrylic rosin resin (the preparation is the same as S1 in Example 1).

[0100] In this comparative example, the soldering flux is calculated by weight and includes:

[0101] 50 parts of acrylic rosin resin, 18 parts of stearic acid, 15 parts of zinc chloride, 5 parts of ethylene glycol monobutyl ether, and 15 parts of isopropanol.

[0102] Comparative Example 3

[0103] A production process of tinned copper wire, different from that of Example 1 in that the composition of the soldering flux is different, and the modified rosin resin in the composition is replaced with a mixture of hydrogenated rosin resin and 2-mercaptobenzimidazole (the mass ratio of hydrogenated rosin resin to 2-mercaptobenzimidazole is 1:0.62).

[0104] In this comparative example, the soldering flux is calculated by weight and includes:

[0105] 50 parts of a mixture of hydrogenated rosin resin and 2-mercaptobenzimidazole, 18 parts of stearic acid, 15 parts of zinc chloride, 5 parts of ethylene glycol monobutyl ether, and 15 parts of isopropanol.

[0106] Experimental Example

[0107] The tensile strength and elongation of the tinned copper wires produced in Example 1 and Comparative Examples 1-3 were detected. In addition, the surface of the copper wires was observed to check whether there were any phenomena on the tin layer. The detection of tensile strength and elongation refers to GB / T 228.1-2021 "Metallic materials - Tensile testing"; the adhesion experiment refers to the standard GB / T 4909.11-2009 "Test methods for bare wires".

[0108] Table 1 Detection results of tinned copper wires produced by different methods

[0109]

[0110] It can be seen from the above detection results that the tinned copper wires produced by using the process of the present invention have higher mechanical strength, are not prone to tin stripping, and have good adhesion of the tin layer. Therefore, it can be shown that the production process of the present invention can avoid tin layer peeling off and enhance the strength performance of the copper wires.

[0111] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0112] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A production process for tinned copper wire to prevent the tin coating from falling off, characterized in that: The following steps are involved: Step 1: Material preparation: Choose pure copper wire and anneal it in a high-temperature furnace; Step 2: Pre-treatment: The annealed copper wire is immersed in the flux and then placed in an oven for drying to obtain the pre-treated copper wire; Step 3: Tinning: The pre-treated copper wire is placed in a tinning furnace for tinning to obtain the pre-treated tinned copper wire; Step 4: Post-processing: The pretreated tinned copper wire is placed in clean water again to wash away impurities, and then vacuum dried to obtain the tinned copper wire; The components of the soldering flux in step 2 are calculated by weight and include: 40-60 parts of modified rosin resin, 16-20 parts of lubricant, 12-18 parts of metal chloride, 3-8 parts of dispersant and 10-20 parts of solvent; The preparation method of the modified rosin resin comprises: S1, weigh hydrogenated rosin resin and epoxy resin, mix them, add a catalyst, heat them to 80-100°C under the protection of nitrogen, stir and react for 3-6 hours, add acrylic acid monomer, continue to react for 2-5 hours, end the reaction, cool to room temperature, and obtain acrylic rosin resin; S2. Mix the acrylic rosin resin and anhydrous ethanol, add 2-mercaptobenzimidazole, stir well until uniform, then add a photoinitiator, react under ultraviolet light at room temperature, stir for 2-4 hours, and remove the ethanol under reduced pressure after the reaction to obtain a modified rosin resin.

2. A production process for tinned copper wire to prevent the tin coating from falling off according to claim 1, characterized in that: In the step 1, the annealing temperature is 650-720° C. and the time is 1-2 hours.

3. A production process for tinned copper wire to prevent the tin coating from falling off according to claim 1, characterized in that: In step 2, the temperature in the oven is 80-90° C., and the drying time is 1-2 hours.

4. A production process for tinned copper wire to prevent the tin coating from falling off according to claim 1, characterized in that: In step 3, the temperature in the tinning furnace is 230-250° C., and the residence time is 2-5 seconds.

5. The production process of tinned copper wire for preventing the tinned layer from falling off according to claim 1, characterized in that: The metal chloride salt is one or more combinations of zinc chloride, magnesium chloride, samarium chloride and sodium chloride.

6. A production process for tinned copper wire to prevent the tin coating from falling off according to claim 1, characterized in that: The lubricant is hexadecanoic acid or octadecanoic acid; the dispersant is ethylene glycol butyl ether or propylene glycol butyl ether; and the solvent is one of isopropanol, toluene and ethyl acetate.

7. A production process for tinned copper wire to prevent the tin coating from falling off according to claim 1, characterized in that: In S1, the amount of the catalyst added is 3%-8% of the mass of the hydrogenated rosin resin; the mass ratio of the hydrogenated rosin resin, the epoxy resin and the acrylic acid monomer is 1:3.5-4.2:0.63-0.

96.

8. The production process of tinned copper wire for preventing the tinned layer from falling off according to claim 1, characterized in that: In the S2, the mass ratio of acrylic rosin resin, 2-mercaptobenzimidazole and anhydrous ethanol is 1:0.31-0.62:4-6; the photoinitiator is benzoin ethyl ether, and the added amount is 2%-8% of the mass of the acrylic rosin resin.

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