Foaming slurry and coating process

Abstract

The invention provides foaming slurry and a coating process. The foaming slurry comprises water, a polymer and a foaming agent. The foaming agent is of a core-shell structure. The core-shell structure comprises a shell, a sealed containing space is defined by the shell, and an expansion object is arranged in the containing space. Wherein the foaming agent is used for switching from the first state to the second state. When the foaming agent is in the first state, the expansion object is in a liquid state, and the volume of the containing space is the first volume. And when the foaming agent is in the second state, the expansion object is gaseous, and the volume of the accommodating space is the second volume. When the foaming agent is switched from the first state to the second state, the expansion object and the shell are expanded, and the second volume is larger than the first volume. The foaming agent is added into the foaming slurry, and the volume of the foaming agent is expanded when the foaming agent is heated, so that defects on the surface of the to-be-coated object are filled. And in addition, the expansion object is always sealed in the shell, and the reaction is irreversible after expansion, so that the defect surface does not collapse after expansion, and the filling effect is good.

Description

Technical Field

[0001] The present application relates to the technical field of leather manufacturing, and particularly relates to a foaming slurry and a finishing process. Background Art

[0002] Leather is a natural material. During the breeding period of animals, phenomena such as grass thorns and lice bites may occur. After the wounds heal, they form grass thorn injuries and lice bite injuries that are often encountered in later leather manufacturing. Coupled with skip knife injuries and burnt surfaces that may occur during mechanical operations such as hair removal and fleshing, leather defects have always been an inevitable loss in the leather processing process. In order to improve the utilization rate of leather, covering and eliminating leather defects has become an important task in the finishing stage.

[0003] Usually, the leather embryo is first spot-filled or scraped, and then roller-filled on the whole surface to further treat the defects. However, the injury repair paste for filling defects is mostly composed of resin and fillers, which only physically fills the defects. It is easy to collapse after drying, and cannot cover large defects. Moreover, the finished leather has a dry and shriveled feel, and the defects are easy to appear.

[0004] Therefore, it is necessary to design a foaming slurry and a finishing process to solve the above technical problems. Summary of the Invention

[0005] The present application provides a foaming slurry and a finishing process with good filling effect.

[0006] According to the first aspect of the embodiments of the present specification, a foaming slurry is provided, which includes water, a polymer, and a foaming agent; the foaming agent has a core-shell structure, the core-shell structure includes an outer shell, the outer shell encloses a sealed accommodation space, and an expandable substance is arranged in the accommodation space; [[ID=2N]]

[0007] Wherein the foaming agent is used to switch from a first state to a second state; when the foaming agent is in the first state, the expandable substance is in a liquid state, and the volume of the accommodation space is a first volume; when the foaming agent is in the second state, the expandable substance is in a gaseous state, and the volume of the accommodation space is a second volume; when the foaming agent switches from the first state to the second state, the expandable substance and the outer shell expand, and the second volume is greater than the first volume. In this way, the foaming agent expands in volume when heated to fill the defects on the surface of the object to be coated. In addition, since the expandable substance is always enclosed in the outer shell and the reaction is irreversible after expansion, it is ensured that the surface of the defect does not collapse after expansion, and it has the advantage of good filling effect.

[0008] Furthermore, the material of the outer shell is polyurethane resin, and the expandable substance is a liquid alkane gas. In this way, during the switching process from the first state to the second state, the outer shell is always in a sealed state, that is, it is ensured that the outer shell is always in an expanded state, and the defects on the leather will not collapse.

[0009] Further, the diameter of the outer shell in the first state ranges from 10 to 40 μm; the diameter of the outer shell in the second state ranges from 30 to 200 μm. In this way, filling for different disabilities can be satisfied.

[0010] Further, by mass, the foaming slurry includes: 50 - 100 parts by weight of water; 10 - 30 parts by weight of a foaming agent; 32.5 - 115 parts by weight of a polymer;

[0011] Among them, the 32.5 - 115 parts by weight of the polymer includes 15 - 45 parts by weight of a polyurethane resin; 10 - 30 parts by weight of an acrylate; 5 - 15 parts by weight of titanium dioxide; 1 - 10 parts by weight of a wetting agent; 0.5 - 5 parts by weight of an alkali - swellable thickener; 1 - 10 parts by weight of a softening aid. In this way, titanium dioxide is used to increase the fineness and covering power of the foaming slurry. The wetting agent is used to promote the fusion between different materials in the foaming slurry. The alkali - swellable thickener is used to adjust the viscosity of the foaming slurry for easy roll - coating operation. The softening aid is used to increase the softness of the foaming slurry and reduce the plastic feeling.

[0012] Further, the polyurethane resin includes polyester - type polyurethane and polycarbonate - type polyurethane; among them, the 15 - 45 parts by weight of the polyurethane resin includes 10 - 30 parts by weight of polyester - type polyurethane; 5 - 15 parts by weight of polycarbonate - type polyurethane. In this way, polyester - type polyurethane has the advantages of strong film - forming flexibility and strong embossing fixity, and can well wrap the foaming agent. Polycarbonate - type polyurethane has the advantage of high strength and can enhance the drop - resistance and abrasion - resistance of the foaming slurry on the leather surface.

[0013] Further, the foaming slurry, by mass, further includes one or more of 10 - 50 parts by weight of a paraffin emulsion, 0.5 - 5 parts by weight of a preservative, and 0.5 - 5 parts by weight of a pH regulator. In this way, the paraffin emulsion is used to enhance the release property of the leather after high - temperature foaming. The preservative is used to prevent the foaming material from spoiling and extend the service time. The pH regulator is used to adjust the pH value of the foaming slurry to achieve a better construction effect.

[0014] According to the second aspect of the embodiments of this specification, a finishing process is provided. Using the foaming slurry described in the first aspect above, it includes the following steps:

[0015] (1) Provide an object to be coated;

[0016] (2) Roll - coat the foaming slurry on the surface of the object to be coated;

[0017] (3) Spray isolating nitrocellulose on the surface of the object to be coated;

[0018] (4) Place the object to be coated into a passing roll press that has been heated to a preset temperature, and apply a preset pressure to the object to be coated. In this way, when the foaming agent contacts the roll press plate, its volume expands due to heat and fills the defects on the surface of the object to be coated.

[0019] Further, the foaming slurry and the isolating nitrocellulose act on the upper surface of the object to be coated; the passing roll press is provided with double drums and clamps the upper and lower surfaces of the object to be coated. In this way, the repair area is increased and the integrity of the object to be coated is ensured.

[0020] Further, before step (1), the finishing process further includes successively drying, standing still, and leather grinding the object to be coated; wherein the drying process uses the board stretching drying method, the clamping distance is 5 - 10 cm, the temperature range is between 40 - 60 °C, and the standing still time is 8 - 24 hours. In this way, the defect repair effect of the subsequent object to be coated can be further improved.

[0021] Further, in step (2), the coating amount of the foaming slurry is 1 - 12 g / sf. In this way, it can ensure that the defects are completely covered and improve the defect repair effect on the leather surface.

[0022] Further, in step (4), the preset temperature range of the roll press is 100 - 180 °C, and the preset pressure range is 50 - 180 kg. In this way, the reaction efficiency of the foaming agent can be improved and the defect repair effect can be enhanced.

[0023] Further, after step (4), the finishing process further includes the following steps:

[0024] Soften the object to be coated;

[0025] Apply an adhesive layer on the surface of the object to be coated;

[0026] Topcoat polyurethane on the surface of the adhesive layer;

[0027] Under the action of a preset temperature and a preset pressure, perform ironing on the object to be coated.

[0028] Further, the adhesive layer includes a composite material of polymer resin, wax emulsion, silicone feel agent, and aziridine crosslinking agent; the preset temperature range for ironing is 70 - 150 °C, and the preset pressure range is 10 - 120 kg, where the temperature and pressure during the ironing operation are less than those during the roll press operation. In this way, on the one hand, the hand feeling and effect can be enhanced, and on the other hand, the coating protection can be enhanced to improve the durability of the cowhide.

[0029] The present application has the following beneficial effects: By adding a foaming agent to the foaming slurry, the foaming agent expands in volume when heated, filling the injuries on the surface of the object to be coated. In addition, since the expanded material is always enclosed within the outer shell and the reaction is irreversible after expansion, it is ensured that the surface of the injury does not collapse after expansion, having the advantage of good filling effect.

[0030] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with this specification and used together with the specification to explain the principles of this specification.

[0032] Figure 1 It is a schematic diagram of the expansion of the foaming agent in the foaming slurry of the present application.

[0033] Figure 2 It is a schematic flow diagram of the coating process of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Here, the technical solutions in the embodiments (or "embodiment modes") of the present application will be clearly and completely described in conjunction with the drawings. When the following description involves the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0035] If there are terms related to directional indications or positional relationships in the embodiments of the present application (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationships and motion conditions between components in a specific posture (as shown in the drawings); if this specific posture changes, then the directional indication or positional relationship will also change accordingly. In addition, the terms "first", "second", etc. involved in the embodiments of the present application are only for the purpose of convenient description and cannot be understood as indicating or implying relative importance.

[0036] Next, the embodiments of this specification will be described in detail.

[0037] The present application discloses a foaming slurry. Calculated by mass fraction, the raw materials for preparing the foaming slurry include the following components: 50 - 100 parts by weight of water; 32.5 - 115 parts by weight of polymer; 10 - 30 parts by weight of foaming agent. The foaming slurry acts on the injuries on the object to be coated. In this embodiment, the object to be coated is leather.

[0038] Calculated by weight, 32.5-115 parts by weight of the polymer includes the following components: 15-45 parts by weight of polyurethane resin; 10-30 parts by weight of acrylate; 5-15 parts by weight of titanium dioxide; 1-10 parts by weight of wetting agent; 0.5-5 parts by weight of alkali swelling thickener; and 1-10 parts by weight of softening aid.

[0039] Among the above raw materials, polyurethane resins include polyester polyurethanes and polycarbonate polyurethanes. Polyester polyurethanes offer the advantages of strong film-forming flexibility and strong embossing properties, allowing them to effectively encapsulate the foaming agent. Polycarbonate polyurethanes offer the advantage of high strength, enhancing the drop and abrasion resistance of the foamed slurry on the leather surface. The 15-45 parts by weight of polyurethane resin comprises 10-30 parts by weight of polyester polyurethane and 5-15 parts by weight of polycarbonate polyurethane.

[0040] Among the above raw materials, acrylates are used to enhance the adhesion of the foaming slurry and the adhesion between the coating and the leather surface after foaming. Titanium dioxide is used to increase the fineness and hiding power of the foaming slurry. The wetting agent is used to promote the integration of different materials in the foaming slurry. The alkali-swelling thickener is used to adjust the viscosity of the foaming slurry to facilitate roller coating. The softening agent is used to increase the softness of the foaming slurry and reduce the plastic feeling.

[0041] Reference Figure 1 As shown, the foaming agent is a core-shell structure, which includes an outer shell, which encloses a sealed accommodation space, and an expansion material is arranged in the accommodation space. In this embodiment, the outer shell is made of polyurethane resin and the expansion material is liquid alkane gas.

[0042] The foaming agent is used to switch from a first state to a second state. When the foaming agent is in the first state, the expansion material is liquid, and the volume of the accommodation space is the first volume. When the foaming agent is in the second state, the expansion material is gaseous, and the volume of the accommodation space is the second volume. During the process of switching from the first state to the second state, the expansion material and the outer shell expand, and the second volume is greater than the first volume. During the switching process from the first state to the second state, the outer shell remains sealed, ensuring that the outer shell remains in an expanded state and that any damage to the leather does not collapse.

[0043] The first state refers to the state where the foaming agent is at room temperature and has not been heated, and the second state refers to the state where the foaming agent is at a temperature of 100°C to 180°C. The diameter of the shell in the first state ranges from 10 to 40 μm, and the diameter of the shell in the second state ranges from 30 to 200 μm.

[0044] In some cases, the foaming slurry also includes one or more of paraffin emulsion, preservatives, and pH regulators. The specific amount can be adjusted based on the cost and effect of use, and is not limited here.

[0045] In this embodiment, the foaming slurry includes paraffin emulsion, preservative and pH regulator. In parts by weight, the foaming slurry includes: 10-50 parts by weight of paraffin emulsion, 0.5-5 parts by weight of preservative, and 0.5-5 parts by weight of pH regulator.

[0046] Among the above raw materials, paraffin wax emulsion is used to enhance the release properties of leather after high-temperature foaming. Preservatives are used to prevent the foaming material from spoiling and extending its service life. pH adjusters are used to adjust the pH value for optimal application results, generally between 5.5 and 8.5 to ensure compatibility with the pH value of the leather itself and ensure the stability of the foaming slurry during contact with the leather. The pH value of the leather itself ranges from 4 to 6.

[0047] Reference Figure 2 As shown, the present application also discloses a finishing process, which uses the above-mentioned foaming slurry and includes the following steps:

[0048] (1) Provide an object to be coated.

[0049] In this embodiment, the object to be coated is leather, and there are scratches on the surface of the leather.

[0050] (2) Roller-coat the foaming slurry on the surface of the object to be coated.

[0051] The foaming slurry is applied in an amount of 1-12 g / sf, such as 1 g / sf, 2 g / sf, 8 g / sf, or 10 g / sf. The roller coating is applied to the entire surface of the object to be coated, thereby ensuring that the damage is completely covered and improving the repair effect on the leather surface. In this embodiment, the foaming slurry is applied to the surface of the leather.

[0052] (3) Spray isolation nitrocellulose on the surface of the object to be coated.

[0053] The isolation nitrocellulose is water-based nitrocellulose. The nitrocellulose in the nitrocellulose can play an anti-sticking role, thereby increasing the embossing release during subsequent leather surface operations and avoiding leather contamination in subsequent steps. The isolation nitrocellulose acts on the surface of the leather.

[0054] (4) A roller press heated to a preset temperature is placed against the surface of the object to be coated, and a preset pressure is applied to the object to be coated.

[0055] The roller press features two rollers, one clamped between the upper and lower surfaces of the object being coated. During operation, the roller press is applied at a preset temperature range of 100-180°C and a preset pressure range of 50-180 kg. For example, at 150°C and 150 kg of pressure, the roller press acts on the upper and lower surfaces of the object being coated, ensuring that the foaming slurry fully reacts and fills any imperfections.

[0056] Before step (1), the finishing process also includes successively drying, standing still, and buffing the object to be coated. Among them, the drying process uses the stretching board drying method, with a clamping distance of 5 - 10 cm and a temperature range of 40 - 60 °C to improve the leather yield. The standing still time is 8 - 24 hours to prepare for subsequent finishing operations. Buffing is carried out using 200 - grit, 260 - grit, or 320 - grit sandpaper to grind the surface of the leather embryo to remove stains and superficial injuries on the surface.

[0057] After step (4), the finishing process also includes the following steps:

[0058] Softening the object to be coated.

[0059] Applying an adhesive layer on the surface of the object to be coated.

[0060] Top - coating polyurethane on the surface of the adhesive layer.

[0061] Under the action of a preset temperature and a preset pressure, perform ironing on the object to be coated.

[0062] In the above process, softening can loosen the cowhide fibers on the leather and make the leather surface uniform. The tool used for softening is a rotating drum, and the softening time is 4h - 24h, which can be adjusted specifically according to the softness requirements of the leather, the size of the leather, and the strength, etc., and is not limited specifically here.

[0063] In the above process, the adhesive layer includes a composite material of polymer resin, wax emulsion, silicone feel agent, and aziridine cross - linker. Here, the adhesive layer serves as an intermediate layer, bonding the foaming slurry layer below and the polyurethane top - coating layer above to improve the stability of the polyurethane on the leather surface.

[0064] In the above process, the polyurethane uses a polyurethane resin with a content of 25%, and the sizing amount is 2g / sf - 5g / sf. By top - coating polyurethane, on the one hand, it can enhance the hand feeling and effect, and on the other hand, it can enhance the coating protection and improve the durability of the cowhide.

[0065] In the above process, the preset temperature range for ironing is 70 °C - 150 °C, and the preset pressure range is 10 kg - 120 kg. Among them, the temperature and pressure during the ironing operation are less than those during the roller press operation. Through the ironing operation, the cross - linking degree, flatness, and gloss of the coating can be enhanced.

[0066] In this application, by adding a foaming agent to the foaming slurry, the foaming agent expands in volume when heated to fill the injuries on the surface of the object to be coated. In addition, due to the fact that the expanding substance is always enclosed in the shell, and has characteristics such as irreversible reaction after expansion, non - collapse after expansion, and good impact resistance, it further ensures that the injured surface does not collapse after expansion, has a high degree of uniformity, and the utilization rate (cutting rate) is significantly improved, having the advantage of good filling effect.

[0067] It should be noted that the technical solutions or technical features described in the above embodiments can be combined or supplemented with each other without conflict. The scope of protection of this application is not limited to the exact structures described in the above embodiments and shown in the drawings; any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the scope of protection of this application.

Claims

1. A foaming slurry, characterized in that, It includes water, a polymer and a foaming agent; the foaming agent has a core-shell structure, the core-shell structure includes a shell, the shell encloses a sealed accommodation space, and an inflatable substance is arranged in the accommodation space; wherein the foaming agent is used to switch from a first state to a second state; when the foaming agent is in the first state, the inflatable substance is in a liquid state, and the volume of the accommodation space is a first volume; when the foaming agent is in the second state, the inflatable substance is in a gaseous state, and the volume of the accommodation space is a second volume; during the process of the foaming agent switching from the first state to the second state, the inflatable substance and the shell expand, and the second volume is greater than the first volume.

2. The foaming slurry according to claim 1, wherein the material of the shell is polyurethane resin, and the inflatable substance is a liquid alkane gas.

3. The foaming slurry according to claim 1, wherein the diameter range of the shell in the first state is 10-40 μm; the diameter range of the shell in the second state is 30-200 μm.

4. The foaming slurry according to claim 1, wherein by mass, the foaming slurry includes: 50-100 parts by weight of water; 10-30 parts by weight of foaming agent; 32.5-115 parts by weight of polymer; wherein the 32.5-115 parts by weight of polymer includes 15-45 parts by weight of polyurethane resin; 10-30 parts by weight of acrylate; 5-15 parts by weight of titanium dioxide; 1-10 parts by weight of wetting agent; 0.5-5 parts by weight of alkali-swellable thickener; 1-10 parts by weight of softening aid.

5. The foaming slurry according to claim 4, wherein the polyurethane resin includes polyester-based polyurethane and polycarbonate-based polyurethane; wherein the 15-45 parts by weight of polyurethane resin includes 10-30 parts by weight of polyester-based polyurethane; 5-15 parts by weight of polycarbonate-based polyurethane.

6. The foaming slurry according to claim 4, wherein the foaming slurry, by mass, further includes one or more of 10-50 parts by weight of paraffin emulsion, 0.5-5 parts by weight of preservative, and 0.5-5 parts by weight of pH regulator.

7. A finishing process, characterized in that, Using the foaming slurry according to any one of claims 1-6 above, it includes the following steps: (1) Provide an object to be coated; (2) Roll-coat the foaming slurry on the surface of the object to be coated; (3) Spray isolating nitrocellulose on the surface of the object to be coated; (4) Place the object to be coated into a through-type rolling press heated to a preset temperature, and apply a preset pressure to the object to be coated.

8. The coating process according to claim 7, wherein the foaming slurry and the isolating nitrocellulose act on the upper surface of the object to be coated; the through-type rolling press is provided with double rollers and clamps the upper and lower surfaces of the object to be coated.

9. The coating process according to claim 7, wherein Before step (1), the finishing process further includes successively drying, standing still, and buffing the object to be coated; wherein the drying process uses the board stretching drying method, the clamping distance is 5 - 10 cm, the temperature range is between 40 - 60 °C, and the standing still time is 8 - 24 hours.

10. The finishing process according to claim 7, wherein in step (2), the coating amount of the foaming slurry is 1 - 12 g / sf.

11. The finishing process according to claim 7, wherein in step (4), the preset temperature range of the roll press is 100 - 180 °C, and the preset pressure range is 50 - 180 kg.

12. The finishing process according to claim 7, characterized in that, After step (4), the finishing process further includes the following steps: softening the object to be coated; coating an adhesive layer on the surface of the object to be coated; top coating polyurethane on the surface of the adhesive layer; performing ironing operation on the object to be coated under the action of preset temperature and preset pressure.

13. The finishing process according to claim 12, wherein the adhesive layer includes a composite material of polymer resin, wax emulsion, silicone feel agent, and aziridine crosslinking agent; the preset temperature range of the ironing is 70 - 150 °C, and the preset pressure range is 10 - 120 kg, wherein the temperature and pressure during the ironing operation are less than the temperature and pressure during the roll press operation.

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