Low-modulus muscle-like synthetic leather as well as preparation method and application thereof

Abstract

The invention provides low-modulus muscle-like synthetic leather as well as a preparation method and application thereof. The low-modulus muscle-like synthetic leather comprises a wet-process base layer, a bonding layer and a dry-process surface layer which are sequentially stacked, the wet-process substrate layer is provided with a submicron needle-cluster-shaped microporous structure of which the interior is communicated, and the wet-process substrate layer is formed by wet-process solidification of slurry containing polyether polyurethane resin, cellulose powder and an amphiphilic modified polysiloxane pore structure regulator; the bonding layer is formed by curing semi-polyester and semi-polyether type polyurethane resin, and the mass ratio of a polyester chain segment to a polyether chain segment in the semi-polyester and semi-polyether type polyurethane resin is (1.2-1.8): 1; and the dry-method surface layer is formed by curing water-based polycarbonate polyurethane resin which takes polypropylene carbonate glycol as a soft segment. According to the low-modulus muscle-like synthetic leather disclosed by the invention, the peel strength and the folding resistance are remarkably improved while the low modulus is maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to a synthetic leather and a preparation process thereof, in particular to a low modulus muscle type synthetic leather, a preparation method and application thereof, and belongs to the technical field of high polymer composite material preparation. BACKGROUND

[0002] With the improvement of consumer demand for comfort of artificial leather products, the development of super soft synthetic leather with real leather texture has become an industry trend. A key indicator to measure the softness of synthetic leather is modulus, and low modulus usually means that the material is softer and more skin-friendly. However, in the existing wet polyurethane synthetic leather manufacturing technology, it is difficult to achieve low modulus and high physical properties at the same time.

[0003] The wet base of traditional soft synthetic leather usually adopts a single polyether or polyester system, and the pores formed during the coagulation process are mostly coarse vertical finger-shaped pores or up-and-down through pores. Although this structure is breathable, it has poor mechanical support. When the resin modulus is reduced in pursuit of softness, the coarse pore walls are prone to collapse, resulting in a significant decrease in the peel strength of the material, and the occurrence of loose surface or hardening phenomenon.

[0004] In addition, in order to obtain a smooth surface touch, the face layer usually uses a higher hardness polycarbonate or polyurethane resin. When the high modulus face layer is directly bonded with the ultra-low modulus wet base, due to the large difference in deformation ability between the two, a large shear stress will be generated at the interface when bending under stress, resulting in poor interlayer adhesion and easy delamination.

[0005] In addition, when preparing super soft synthetic leather materials, if the conventional high-temperature drying process is used, the rapid evaporation of the solvent will cause the collapse of the fragile microporous framework, and if the vehicle speed or temperature is reduced, it will result in low production efficiency or excessive residual solvent, affecting the hygiene performance and hand feeling of the finished product.

[0006] Therefore, it is urgent to develop a new type of synthetic leather and a preparation method thereof which can reconstruct the wet microporous structure and significantly improve the peel strength and folding resistance while maintaining low modulus. SUMMARY

[0007] Based on the above background, the purpose of the present application is to provide a low modulus muscle type synthetic leather, a preparation method and application thereof, which solves the technical problems of low peel strength, poor interlayer adhesion and slightly hard hand feeling of existing soft synthetic leather.

[0008] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0009] A low modulus muscle-like synthetic leather, comprising a wet base layer, a bonding layer and a dry surface layer which are sequentially stacked; the wet base layer has an internally connected sub-micron needle cluster-like microporous structure, and the wet base layer is formed by wet coagulation of a slurry containing polyether polyurethane resin, cellulose powder and amphiphilic modified polysiloxane pore structure regulator; the bonding layer is formed by curing of a semi-polyester semi-polyether polyurethane resin, the mass ratio of polyester segment to polyether segment in the semi-polyester semi-polyether polyurethane resin is (1.2-1.8):1; and the dry surface layer is formed by curing of an aqueous polycarbonate polyurethane resin with polypropylene carbonate glycol as soft segment.

[0010] Preferably, the pore size distribution of the needle cluster-like microporous structure is between 0.1-0.9 μm, and the preparation raw materials of the wet base layer include, by weight parts: polyether polyurethane resin with solid content of 25-30% 100 parts, cellulose powder 30-50 parts, amphiphilic modified polysiloxane pore structure regulator 3-6 parts, dimethylformamide 100-120 parts; wherein the amphiphilic modified polysiloxane pore structure regulator is a modified silicone oil emulsion with amino and / or carboxyl side chains, and the solid content is 20-30%.

[0011] Preferably, the total thickness of the low modulus muscle-like synthetic leather is ≤0.7 mm, the peel strength is ≥20 N / 3 cm, and the softness is ≥7 S; the modulus of the semi-polyester semi-polyether polyurethane resin is between the modulus of the wet base layer and the modulus of the dry surface layer.

[0012] A preparation method of a low modulus muscle-like synthetic leather, comprising the following steps:

[0013] S1, dipping the base cloth in the wet slurry, after coagulation and water washing, sequentially performing pre-drying and main drying to obtain a wet base layer with a needle cluster-like microporous structure;

[0014] S2, coating a surface layer slurry on a release paper, and forming a dry surface layer by gradient drying; then coating a bonding layer slurry on the dry surface layer, and gradient drying to a semi-dry state;

[0015] S3, hot pressing the wet base layer obtained in step S1 and the bonding layer in a semi-dry state in step S2, and after peeling off the release paper, performing embossing treatment to obtain the low modulus muscle-like synthetic leather.

[0016] Preferably, in step S1, the pre-drying temperature is 120-160℃, and the time is 3-5 min; the main drying temperature is 140-160℃, and the time is 5-7 min.

[0017] Preferably, in the step S1, the coagulation liquid used in the coagulation contains 20wt%-25wt% dimethylformamide aqueous solution, and the coagulation temperature is controlled at 25-35 DEG C; the base fabric is applied with a tension of 2-3N before being immersed, and is subjected to a conditioning treatment at a temperature of 55-75 DEG C.

[0018] Preferably, in the step S2, the viscosity of the surface layer sizing agent is 900-1800cps, and the temperature program of the gradient drying is 65 DEG C, 70 DEG C, 80 DEG C, 120 DEG C in sequence; the viscosity of the bonding layer sizing agent is 4000-6000cps, and the temperature program of the gradient drying to a semi-dry state is 110 DEG C, 115 DEG C, 120 DEG C, 120 DEG C, 120 DEG C, 130 DEG C, 130 DEG C in sequence.

[0019] Preferably, in the step S3, the semi-dry state means that the bonding layer surface is free of wet feeling but retains heat adhesion, and the residual solvent content is controlled within the process allowable range; the lamination speed is controlled at 12-15m / min.

[0020] Preferably, in the step S3, the texturing treatment is carried out in a continuous texturing machine, the texturing temperature is 70-80 DEG C, and the single-stage texturing time is 8-10min; an organic silicon softener containing polyether-modified polysiloxane chain segments is added during the texturing treatment.

[0021] The application relates to an application of a low-modulus muscle-like synthetic leather in the preparation of luggage, furniture or automobile seats.

[0022] Compared with the prior art, the application has the following advantages:

[0023] The low-modulus muscle-like synthetic leather of the application uses the hydrogen bond interaction between the amphiphilic groups of the amphiphilic modified polysiloxane pore structure regulator and the molecular chain of the polyurethane to transform the traditional finger-shaped large pores into submicron needle cluster dispersed structures. The structures greatly increase the number of pores in a unit volume, improve the porosity, and endow the material with better softness (the softness is greater than or equal to 7S). Meanwhile, the submicron dense skeleton effectively disperses stress, so that the peeling strength is improved to more than 20N, thereby solving the contradiction between the softness and the strength of the soft synthetic leather.

[0024] The application innovatively introduces a semi-polyester semi-polyether resin as a bonding layer. The high polarity of the polyester chain segment anchors the interface, and the polyether chain segment provides flexibility, so that the semi-polyester semi-polyether resin plays a mechanical buffering role between the super-soft substrate and the smooth surface layer, and overcomes the delamination defect caused by the modulus mismatch.

[0025] The application discloses a preparation method of a low-modulus muscle-like synthetic leather. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0027] Figure 1 is a process flow chart of the preparation method of the low-modulus muscle-like synthetic leather of the present application;

[0028] Figure 2 is a microstructure SEM diagram of a wet base layer prepared in the embodiment 3 of the present application;

[0029] Figure 3 is a microstructure SEM diagram of a section of a traditional wet base. DETAILED DESCRIPTION

[0030] The present application aims to solve the technical contradiction that the peeling strength and softness are difficult to be considered in the existing soft synthetic leather. The inventors have found, through in-depth research, that by introducing a specific amphiphilic modified polysiloxane pore structure regulator into a wet base and cooperating with a pre-drying-main drying grading curing process, the structure limitation of the traditional wet polyurethane vertical finger-shaped pores can be broken, and a sub-micron needle cluster-shaped pore structure can be formed in situ. This structure significantly increases the number of pores in a unit volume, greatly reduces the modulus of the material and improves the softness of the synthetic leather, while retaining a dense skeleton support, thereby maintaining high physical properties.

[0031] Further, in order to solve the problem of poor interlayer adhesion caused by modulus mismatch between the relatively low-modulus super-soft wet base and the relatively high-modulus dry surface layer, the present application creatively introduces a semi-polyester semi-polyether polyurethane as a bonding layer. This resin system has both the flexibility of polyether segments and the strong polarity of polyester segments, builds a modulus gradient transition zone between the layers, and uses a semi-dry lamination process to promote the interpenetration of molecular chains at the interface, thereby realizing firm combination of the interface.

[0032] The present application provides a low modulus muscle-like synthetic leather, comprising a wet base layer, a bonding layer and a dry surface layer arranged in sequence. In the present application, the total thickness of the low modulus muscle-like synthetic leather is ≤0.7mm, the peel strength is ≥20N / 3cm, and the softness is ≥7S. The modulus of the semi-polyester semi-polyether type polyurethane resin is between the modulus of the wet base layer and the modulus of the dry surface layer.

[0033] The wet base layer has an internal communication sub-micron needle cluster-like micropore structure, and the wet base layer is formed by wet coagulation of a slurry containing a polyether type polyurethane resin, cellulose powder and an amphiphilic modified polysiloxane pore structure regulator. In the present application, the pore size distribution of the needle cluster-like micropore structure is between 0.1-0.9μm, and the preparation raw materials of the wet base layer include, by weight: 100 parts of a polyether type polyurethane resin with a solid content of 25-30%, 30-50 parts of cellulose powder, 3-6 parts of an amphiphilic modified polysiloxane pore structure regulator, and 100-120 parts of dimethylformamide. The amphiphilic modified polysiloxane pore structure regulator contains amino or carboxyl groups capable of forming hydrogen bonds with polyurethane molecular chains.

[0034] The bonding layer is cured from a semi-polyester semi-polyether type polyurethane resin, and the mass ratio of polyester segments to polyether segments in the semi-polyester semi-polyether type polyurethane resin is (1.2-1.8):1.

[0035] The dry surface layer is cured from a water-based polycarbonate polyurethane resin with polypropylene carbonate glycol as the soft segment.

[0036] The present application also provides a preparation method of a low modulus muscle-like synthetic leather, comprising the following steps:

[0037] S1, dipping the base cloth in a wet slurry, coagulating and washing with water, and then sequentially performing pre-drying and main drying to obtain a wet base layer with a needle cluster-like micropore structure;

[0038] S2, coating a surface layer slurry on a release paper, and forming a dry surface layer by gradient drying; then coating a bonding layer slurry on the dry surface layer, and gradient drying to a semi-dry state;

[0039] S3, hot pressing the wet base layer obtained in step S1 and the bonding layer in a semi-dry state in step S2, peeling off the release paper, and then performing a rubbing treatment to obtain a low modulus muscle-like synthetic leather.

[0040] In step S1 of the present application, the pre-drying temperature is 120-160℃, and the time is 3-5min; the main drying temperature is 140-160℃, and the time is 5-7min.

[0041] In step S1 of the present application, the coagulating liquid used in coagulation contains 20wt%-25wt% dimethylformamide aqueous solution, and the coagulation temperature is controlled at 25-35℃; the base cloth is applied with tension of 2-3N before impregnation, and is subjected to temperature of 55-75℃ for moisture conditioning treatment.

[0042] In step S2 of the present application, the viscosity of the surface layer sizing material is 900-1800cps, and the temperature program of gradient drying is 65℃, 70℃, 80℃, 120℃ in sequence; the viscosity of the bonding layer sizing material is 4000-6000cps, and the temperature program of gradient drying to semi-dry state is 110℃, 115℃, 120℃, 120℃, 120℃, 130℃, 130℃ in sequence.

[0043] In step S3 of the present application, the semi-dry state means that the bonding layer surface is not wet to touch but remains hot adhesion, and the residual solvent content is controlled within the process allowable range; the lamination speed is controlled at 12-15m / min.

[0044] In step S3 of the present application, the embossing treatment is carried out in a continuous embosser, the embossing temperature is 70-80℃, and the single-stage embossing time is 8-10min; the silicone softener containing polyether modified polysiloxane segment is added in the embossing treatment process.

[0045] The present application also provides a low modulus muscle type synthetic leather in the preparation of luggage, furniture or car seats.

[0046] The technical solutions of the present application will be further described below by specific examples, and in combination with the drawings. It should be understood that the implementation of the present application is not limited to the following examples, and any form of variation and / or change of the present application will fall within the scope of protection of the present application.

[0047] In the present application, unless specified, all parts, percentages are weight units, and the equipment and raw materials used can be purchased from the market or commonly used in the art. The methods in the following examples are conventional methods in the art, unless otherwise specified. The components or equipment in the following examples are general standard components or components known to those skilled in the art, and their structure and principle can be known to the skilled person through technical manual or obtained through conventional experimental methods.

[0048] For ease of understanding, the main raw materials used in the following examples are described as follows, but do not limit the protection scope of the present application.

[0049] Polyether type polyurethane resin: solid content 28%.

[0050] Amphiphilic modified polysiloxane pore structure regulator: preferably use amino / carboxyl amphiphilic group containing side chain silicone oil type protein-like auxiliary, from Huaxin Technology. The auxiliary takes polysiloxane as the main chain, and simulates the amphiphilic characteristics of protein through the amino / carboxyl group in the side chain. Its mechanism is that, on the one hand, the low surface energy of the silicone oil segment promotes the nucleation of micropores; on the other hand, the amino / carboxyl group forms a hydrogen bond with the polyurethane hard segment to physically crosslink and regulate the phase separation speed, thereby forming a special needle cluster structure.

[0051] Semi-polyester semi-polyether type polyurethane resin: solid content 34%, mass ratio of polyester segment to polyether segment about 1.5:1.

[0052] Water-based polycarbonate polyurethane resin: polypropylene carbonate glycol as soft segment, solid content 30%.

[0053] Organic silicon softener: environmentally friendly polyether modified polysiloxane emulsion.

[0054] Example 1

[0055] This example prepares a low modulus leather-like synthetic leather, the specific steps are as follows:

[0056] S1, wet base preparation

[0057] 100 parts of polyether type polyurethane resin, 30 parts of DL-white synthetic cellulose, 3 parts of amphiphilic modified polysiloxane pore structure regulator, 0.3 parts of defoaming agent, 100 parts of DMF are uniformly mixed, and a wet slurry is prepared after degassing. The base fabric (2N tension is applied) is immersed in a 24% DMF aqueous solution, and the pick-up rate is controlled in the appropriate range. Then coat the wet slurry, the scraper gap is 0.8 mm. Enter the coagulation bath containing 20% DMF (temperature 25°C) for coagulation, and then wash in warm water at 45-65°C. First enter the pre-drying section, temperature 120°C, time 3 min; then enter the main drying section, temperature 140°C, time 5 min. A wet base with microporous structure is prepared.

[0058] S2, dry layer and adhesive layer preparation

[0059] Top layer: coat the water-based polycarbonate polyurethane resin (viscosity 900 cps) on the release paper, and dry at 65-120°C in stages.

[0060] Adhesive layer: coat the semi-polyester semi-polyether type polyurethane resin (viscosity 4000 cps) on the top layer, and dry at 110-130°C in stages to semi-dry state.

[0061] S3, lamination and post-processing

[0062] The wet base and the semi-dry adhesive layer are laminated at a car speed of 12 m / min.

[0063] Peel off the release paper, enter the continuous embosser, emboss at 70℃ for 8min, during which spray 2% silicone softener in water solution.

[0064] Example 2

[0065] This example prepares a low modulus muscle-like synthetic leather, the specific steps are the same as example 1, the difference is that:

[0066] In the wet slurry, the cellulose is increased to 40 parts, and the amphiphilic modified polysiloxane pore structure regulator is increased to 4 parts.

[0067] In the drying process, the pre-drying temperature is increased to 140℃, and the time is 4min; the main drying temperature is 150℃.

[0068] In the lamination process, the line speed is adjusted to 13.5m / min, and the bonding layer drying temperature curve is optimized to ensure the interfacial permeability in the semi-dry state.

[0069] Example 3

[0070] This example prepares a low modulus muscle-like synthetic leather, the specific steps are as follows:

[0071] S1, wet base preparation

[0072] Prepare the wet slurry: add 100 parts of polyether polyurethane resin, 40 parts of DL-white synthetic cellulose, 4 parts of amphiphilic modified polysiloxane pore structure regulator, 0.3 parts of defoaming agent, 120 parts of DMF and 5 parts of color paste into the stirring kettle, high-speed dispersion and uniform mixing, and vacuum degassing treatment to prepare a uniform and stable wet slurry.

[0073] The base fabric is immersed in a 25% DMF aqueous solution under the control of 2.5N tension, and then the wet slurry prepared above is coated on the surface of the base fabric, and the gap between the doctor blades is controlled to ensure uniform coating.

[0074] The base fabric coated with the slurry is sent into the coagulation bath, which is a 25% DMF aqueous solution, and the temperature is controlled at 30℃ to make the slurry layer phase separate and coagulate; after coagulation is completed, it enters the multi-stage washing tank, and the residual solvent is washed away in warm water at 50-70℃.

[0075] The wet base first enters the pre-drying section, the temperature is set to 140℃, and the treatment time is 5min, which aims to quickly lock the microporous skeleton and prevent the collapse of the pore wall; then enter the main drying section, the temperature is maintained at 160℃, and the treatment time is 7min, to completely remove the solvent, and a wet base with dense needle cluster-like sub-micron microporous structure is prepared, the microstructure is shown in Figure 2 ​Figure 3 The microstructure of the traditional wet-process base substrate section is shown. It can be seen that the red circle marked area clearly shows the typical finger-shaped large pores in the traditional wet-process polyurethane curing process. The coarse hole structure penetrates the longitudinal section of the substrate. There is a lack of effective transverse connection between the hole walls. When the material is subjected to bending or peeling force, the coarse hole walls are prone to bending and collapse, resulting in low peeling strength of the material, and the hand feeling cannot provide a firm meaty feeling similar to that of real leather. In contrast, the wet-process base substrate section prepared in this embodiment presents small, dense and uniformly distributed needle-shaped or sponge-shaped micropores, and the pore size is significantly reduced.

[0076] S2, dry layer and adhesive layer preparation

[0077] Surface layer: water-based polycarbonate polyurethane resin is scraped on release paper, and the dry coating amount is controlled to be 45 g / m 2 , and then dried and formed into a film by passing through gradient drying ovens at 65°C, 70°C, 80°C and 120°C in sequence.

[0078] Adhesive layer: scrape semi-polyester semi-polyether polyurethane resin on the dried surface layer, control the dry coating amount to be 160 g / m 2 . Then enter the temperature control oven for gradient drying, and the temperature program is set to 110°C, 115°C, 120°C, 120°C, 120°C, 130°C and 130°C in sequence. The drying degree is strictly controlled to make the adhesive layer reach a semi-dry state, that is, the surface is dry to the touch but retains strong heat adhesion.

[0079] S3, lamination and post-processing

[0080] The wet-process base substrate is laminated with the adhesive layer in a semi-dry state. In order to ensure the best interface bonding effect and hand feeling, the lamination speed is controlled to be 15 m / min to prevent the lamination from being not firm due to too fast speed, or the interface from being too hard due to too slow speed.

[0081] The laminated semi-finished product is peeled off from the release paper and sent to a continuous texturing machine for texturing treatment. The texturing temperature is set to 80°C, and each texturing time is 10 min. A water solution containing 2% environmentally friendly organic silicone softener is uniformly sprayed during the texturing process to obtain the finished product.

[0082] Comparative Example 1

[0083] This comparative example prepares a low modulus synthetic leather of the muscle type. The specific steps are the same as those of Example 3, except that:

[0084] The amphiphilic modified polysiloxane pore structure regulator is not added in the wet-process slurry, and the other conditions remain the same.

[0085] Comparative Example 2

[0086] A low modulus muscle-like synthetic leather was prepared in this comparative example, and the specific steps were the same as those in Example 3, except that:

[0087] The pre-drying step was cancelled, and after washing, it was directly put into the main oven at 160°C for one-time drying.

[0088] Comparative Example 3

[0089] A low modulus muscle-like synthetic leather was prepared in this comparative example, and the specific steps were the same as those in Example 3, except that:

[0090] The adhesive layer was replaced by a common polyether polyurethane resin.

[0091] Comparative Example 4

[0092] A low modulus muscle-like synthetic leather was prepared in this comparative example, and the specific steps were the same as those in Example 3, except that:

[0093] The bonding speed was increased to 20 m / min, resulting in excessive solvent residue in the adhesive layer.

[0094] The synthetic leather prepared in the above examples and comparative examples was tested for performance, and the test standards were referred to Table 1.

[0095] Table 1 Test Standards

[0096]

[0097] The results of performance testing of the synthetic leather prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 2.

[0098] Table 2 Summary of Performance Test Results of Examples 1-3 and Comparative Examples 1-4

[0099]

[0100] From the data in Table 2, the softness of Example 3 reaches 7.8S, which is significantly better than Comparative Example 1 (5.0S) and Comparative Example 2 (5.5S). Mechanism analysis shows that Comparative Example 1 lacks an amphiphilic modified polysiloxane pore structure regulator, and its interior is mainly composed of traditional coarse vertical finger-shaped pores. This structure concentrates stress when bending, resulting in a hard hand feeling. In Example 3, the additive is a kind of silicone oil protein-like material, and the polysiloxane backbone provides extremely low surface tension, which promotes the rapid nucleation of micropores. At the same time, the side chain modified protein-like functional groups (amino groups / carboxyl groups) in the polysiloxane backbone have strong hydrogen bond interactions with the polyurethane molecular chain. This structure of silicone oil skeleton and protein-like side chain effectively reduces the entanglement density between the polymer chains, induces the phase separation to develop into a microphase region, and forms a sub-micron needle cluster-shaped micropore. This micropore structure is similar to a honeycomb, which not only provides a large free volume but also maintains the continuity of the skeleton. Comparative Example 2 cancels the pre-drying, resulting in the instantaneous explosive volatilization of the solvent in the wet base at high temperature, and the collapse and coarsening of the pore wall. Not only does this result in a thinning of the thickness, but it also severely damages the mechanical support of the micropores, leading to a significant decrease in the peeling strength. The pre-drying process of Example 3 successfully locks the micropore skeleton before the massive volatilization of the solvent.

[0101] The peeling strength of Example 3 is as high as 28N, while that of Comparative Example 3 is only 12N and shows delamination. This is because Example 3 uses a semi-polyester semi-polyether resin as the adhesive layer. From a molecular level, the polyester segment provides strong polar groups, which can form high-density hydrogen bonds with the base and face layer. The polyether segment imparts flexibility. More importantly, the modulus of this resin is between the ultra-soft wet base and the relatively dense poly-carbon face layer, acting as a mechanical buffer and effectively relieving the stress concentration between the layers. Comparative Example 3 uses a common polyether resin, which has a low modulus and insufficient polarity, and cannot form effective mechanical transmission at the interface, resulting in poor peeling strength.

[0102] Although the peeling strength of Comparative Example 4 is acceptable, the softness decreases sharply to 4.8S, and the hand feeling becomes hard. This is because the speed of Comparative Example 4 is too fast, resulting in excessive solvent residue in the adhesive layer during lamination. Excessive solvent will excessively erode the micropore structure of the wet base during subsequent drying, and even penetrate and fill into the micropores, causing the glue nail effect to be too strong, resulting in a stiff and thick crease in the finished product. Example 3 controls the speed at 15m / min in a semi-dry state, which ensures the diffusion and interpenetration of the molecular chains at the interface, while avoiding excessive penetration of the adhesive layer to damage the flexible structure of the base.

[0103] The principles and implementation modes of the present application are described by applying specific examples in this paper, and the above examples are only used to help understand the method of the present application and its core idea. It should be noted that for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A low-modulus, skin-like synthetic leather, characterized in that: The low-modulus, skin-like synthetic leather comprises a wet-process base layer, an adhesive layer, and a dry-process top layer, which are sequentially stacked. The wet-process base layer has a submicron-sized needle-like microporous structure with internal interconnections, and is formed by wet-process coagulation of a slurry containing polyether-type polyurethane resin, cellulose powder, and an amphiphilic modified polysiloxane pore structure regulator. The adhesive layer is formed by curing a semi-polyester semi-polyether-type polyurethane resin, wherein the mass ratio of polyester segments to polyether segments in the semi-polyester semi-polyether-type polyurethane resin is (1.2-1.8):

1. The dry-process top layer is formed by curing an aqueous polycarbonate polyurethane resin with polypropylene carbonate diol as the soft segment.

2. The low-modulus, muscle-like synthetic leather according to claim 1, characterized in that: The pore size of the needle-like microporous structure is distributed between 0.1 and 0.9 μm. The raw materials for preparing the wet substrate layer include, by weight, 100 parts of polyether polyurethane resin with a solid content of 25-30%, 30-50 parts of cellulose powder, 3-6 parts of amphiphilic modified polysiloxane pore structure regulator, and 100-120 parts of dimethylformamide; wherein, the amphiphilic modified polysiloxane pore structure regulator is a modified silicone oil emulsion with amino and / or carboxyl groups in the side chain, and its solid content is 20-30%.

3. The low-modulus, muscle-like synthetic leather according to claim 1, characterized in that: The total thickness of the low-modulus, skin-like synthetic leather is ≤0.7mm, the peel strength is ≥20N / 3cm, and the softness is ≥7S; the modulus of the semi-polyester, semi-polyether polyurethane resin is between the modulus of the wet-process base layer and the modulus of the dry-process surface layer.

4. A method for preparing low-modulus, muscle-like synthetic leather according to any one of claims 1-3, characterized in that: The method includes the following steps: S1. The base fabric is impregnated in wet slurry, and after coagulation and washing, it is pre-dried and main dried in sequence to obtain a wet base layer with needle-like microporous structure. S2. Coat the release paper with a surface layer paste and dry it in a gradient to form a dry surface layer; then coat the dry surface layer with an adhesive layer paste and dry it in a gradient to a semi-dry state. S3. The wet base layer obtained in step S1 is hot-pressed together with the adhesive layer in the semi-dry state in step S2. After peeling off the release paper, the texture is rubbed to obtain the low-modulus muscle-like synthetic leather.

5. The method for preparing a low-modulus, muscle-like synthetic leather according to claim 4, characterized in that: In step S1, the pre-drying temperature is 120-160℃ and the time is 3-5 minutes; the main drying temperature is 140-160℃ and the time is 5-7 minutes.

6. The method for preparing a low-modulus, muscle-like synthetic leather according to claim 4, characterized in that: In step S1, the coagulation solution used for coagulation contains 20wt%-25wt% dimethylformamide aqueous solution, and the coagulation temperature is controlled at 25-35℃; the base fabric is subjected to a tension of 2-3N before impregnation and is subjected to a humidification treatment at a temperature of 55-75℃.

7. The method for preparing a low-modulus, muscle-like synthetic leather according to claim 4, characterized in that: In step S2, the viscosity of the surface layer slurry is 900-1800 cps, and the temperature program for gradient drying is 65℃, 70℃, 80℃, and 120℃ respectively; the viscosity of the adhesive layer slurry is 4000-6000 cps, and the temperature program for gradient drying to a semi-dry state is 110℃, 115℃, 120℃, 120℃, 120℃, 130℃, and 130℃ respectively.

8. The method for preparing a low-modulus, muscle-like synthetic leather according to claim 4, characterized in that: In step S3, the semi-dry state means that the surface of the adhesive layer is not wet to the touch but retains thermal tack, and the residual solvent content is controlled within the allowable range of the process; the bonding speed is controlled at 12-15m / min.

9. The method for preparing a low-modulus, muscle-like synthetic leather according to claim 4, characterized in that: In step S3, the texturing process is carried out in a continuous texturing machine at a texturing temperature of 70-80℃ and a single-stage texturing time of 8-10 minutes. During the texturing process, an organosilicon softener containing polyether-modified polysiloxane segments is added.

10. The use of the low-modulus, muscle-like synthetic leather according to any one of claims 1-3 in the preparation of bags, furniture or automobile seats.

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