A first bath impregnating solution for two-bath impregnation of fiber reinforcement

Abstract

The present application belongs to the technical field of impregnation liquid, and particularly relates to a first bath impregnation liquid for two-bath impregnation method of fiber framework material. The present application adds active sulfur compound into the first bath impregnation liquid of two-bath impregnation method for the first time, forms a "polysulfide bond-K-R" structure, provides clear chemical crosslinking between the first bath impregnation and the second bath / rubber, and realizes the improvement of peeling force, the adhesion of impregnation and the over-sulfur recession performance. The active sulfur compound of the present application can significantly reduce the addition amount of two main components, i.e. epoxy compound and blocked isocyanate, in the first bath impregnation liquid under the condition of ensuring the initial and over-sulfur adhesion of impregnation, and the solid content can be reduced from more than 3.00% to 2.30-2.80%, which significantly saves the raw material cost on the basis of improving the adhesion of impregnation.

Description

Technical Field

[0001] This invention belongs to the field of impregnation solution technology, specifically relating to a first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials. Background Technology

[0002] Fiber-reinforced reinforcing materials, as key reinforcing components in rubber products, are widely used in industrial fields such as tires, conveyor belts, and hoses. Their core function is to withstand mechanical loads and maintain the dimensional stability of the products. In practical applications, the interfacial adhesion strength between the reinforcing material and the rubber matrix directly determines the durability and safety of the product. Especially for polymer fibers such as polyester and nylon, due to their low surface polarity and strong chemical inertness, it is difficult to form a strong bond with rubber, which has always been a technical challenge for the industry. Traditionally, the industry has generally used a resorcinol-formaldehyde-latex (RFL) impregnation system to treat the fiber surface, achieving adhesion through the physical interaction between the phenolic resin and the fiber and the co-vulcanization reaction between the latex and the rubber. However, the RFL system has significant limitations: on the one hand, resorcinol and formaldehyde are both toxic substances, posing a threat to the health of production personnel and facing application restrictions due to tightening environmental regulations; on the other hand, for materials such as polyester, the adhesion effect of a single RFL system is insufficient, necessitating the use of a two-bath impregnation method, that is, first performing a first bath pretreatment with an epoxy-isocyanate system, and then applying a second bath of RFL. While the two-bath impregnation method, with its multi-step process, can improve adhesion, it also increases energy consumption, equipment complexity, and production costs, thus weakening the cost advantage of polyester materials.

[0003] To circumvent the environmental issues of phenolic resin systems, the inventors of this invention disclosed a non-phenolic environmentally friendly impregnation solution for fiber-reinforced materials in patent application number 202211156718.0. This solution can improve the interaction strength between the impregnating adhesive resin and latex, as well as between the resin and rubber, thereby enhancing overall adhesion. However, due to cost constraints, it has not been industrialized. Therefore, the two-bath impregnation method remains the mainstream method for industrial application, with the key being whether it can improve the adhesion retention (resistance to over-sulfurization degradation) of rubber products in the later stages of vulcanization (i.e., under over-sulfurization conditions). In this regard, although the inventors of this invention added sulfur-containing compounds to the second bath of the one-bath or two-bath impregnation solution, which can chemically bond with the phenolic adhesive resin and simultaneously chemically bond with the rubber and latex through sulfur bonds, effectively improving the interaction strength between the impregnating resin and the rubber. However, the sulfur-containing compounds account for up to 20% of the dry weight. Therefore, if such a high content of sulfur-containing compounds is added to the first bath of the two-bath impregnation solution, the following problems will inevitably occur: (1) Some groups of sulfur-containing compounds (such as hydroxyl groups) will form a competitive reaction with the end groups on the polyester surface, resulting in insufficient activation of the polyester surface; (2) A high amount of sulfur-containing compounds may lead to excessive cross-linking between the rubber and the impregnation layer, as well as the rubber itself, which may cause the adhesive interface layer to harden and become brittle, and reduce its flexibility. During dynamic fatigue or flexing, the brittle interface is more likely to generate microcracks, leading to premature decay of adhesive force, or even brittle peeling of the interface; (3) Increased production costs. It should also be noted that although the solid content of the first bath in a two-bath process is usually not high (generally below 6.50%, with a minimum of about 3.00%), performance decreases as the solid content decreases, thus there is a significant lower limit to cost reduction through lowering the solid content in actual production. However, the epoxy monomers and blocked isocyanate monomers used often involve fine purification and water dispersion pretreatment, resulting in considerable costs. Reducing their dosage may lead to a precipitous drop in adhesive performance. Therefore, in conventional RFL two-bath process formulations, reducing the solid content of the first bath not only leads to a decrease in cord adhesive performance but also makes it difficult to further reduce costs.

[0004] Therefore, it is necessary to develop a first-bath impregnation solution that can significantly reduce costs with only a small amount of additives while ensuring adhesive performance and better addressing the degradation caused by oversulfurization of cords. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the existing RFL two-bath method, such as severe over-sulfurization of the first bath impregnation solution, which easily leads to delamination of the cord, and reduced solid content of the first bath impregnation solution, which easily leads to decreased cord bonding performance and difficulty in reducing costs. The present invention provides a first bath impregnation solution for the two-bath impregnation method of fiber skeleton materials.

[0006] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution: A first bath impregnation solution for a two-bath impregnation method for fiber-reinforced materials. The first impregnation bath uses water as a solvent and includes epoxy compounds, blocked isocyanate compounds, and active sulfur-containing compounds; the solid content of the first impregnation bath is 1.00~5.00%; the weight of the active sulfur-containing compounds is 0.50~5.00% of the dry weight of the first impregnation bath; wherein, by weight, the dry weight of the first impregnation bath includes: 55-80 parts of blocked isocyanate compounds, 15-40 parts of epoxy compounds, and 0.05-10 parts of active sulfur-containing compounds.

[0007] Because the urethane bonds and other components in the crosslinking network of the first bath in the two-bath process are prone to breakage under prolonged heating and the action of vulcanization accelerators, the adhesive strength decreases significantly, increasing the risk of cord delamination. To achieve basic adhesion requirements, the traditional two-bath process requires the first bath impregnation solution to maintain a certain solid content (minimum approximately 3.00%, generally below 6.50%, with performance decreasing as solid content decreases). However, the main components used, such as epoxy resin and blocked isocyanate, are expensive. Further reducing the solid content to control costs often sacrifices adhesive performance, creating a performance-cost dilemma. Existing improvement schemes mostly focus on the second bath or high-solids-content systems, such as adding a large amount (e.g., 3.00%-20.00% by dry weight) of active sulfur compounds to enhance the crosslinking of latex and rubber. However, this is costly, and the application methods for active sulfur compounds in the second bath are difficult to directly apply to the low-solids-content first bath impregnation solution. This is because the first bath impregnation solution has a small amount of adhesive applied and is component-sensitive; blindly adding a large amount of active sulfur compounds may lead to system instability or poor performance. How to significantly reduce the solid content and the amount of active sulfur compounds added in the first bath of adhesive solution while ensuring or even improving the adhesive performance, so as to reduce raw material consumption and save costs, has become an urgent need.

[0008] In existing technologies, while active sulfur compounds have been proven to form chemical bonds with rubber through sulfur bonds, thereby improving adhesive durability, their application is mostly limited to the second bath impregnation solution or the one-bath system, and the amount of active sulfur compounds added is relatively high, aiming to achieve performance enhancement through extensive cross-linking. However, this "high input, high output" model is not suitable for the first bath impregnation solution, because the first bath impregnation solution itself has a low solid content. If a strategy of adding a large amount of active sulfur compounds is chosen, not only will the cost be prohibitive, but the stability and permeability of the impregnation solution may also be affected due to component imbalance. This invention controls the weight of the active sulfur-containing compound to 0.50-5.00% of the dry weight of the first bath impregnation solution. This ensures that the amount of active sulfur-containing compound added to the first bath impregnation solution is much lower than the common addition amount (5.00-15.00%) in the second bath system, while still matching the low solid content (1.00%-5.00%) of the first bath. This allows the active sulfur-containing compound to both bond with epoxy or isocyanate groups and embed itself in the crosslinking network of the first bath, and to interact with rubber molecules during the vulcanization stage, preventing over-crosslinking. Simultaneously, the extremely low addition amount of the active sulfur-containing compound allows for a suitable reduction in the solid content of the first bath impregnation solution or the amount of other components while maintaining performance, thereby optimizing overall cost. The formulation components designed in this invention not only maintain the chemical balance of the first bath impregnation solution system but also provide additional chemical bridging at the interface through the potential crosslinking of the rubber with the sulfur bonds of the active sulfur-containing compound, thus compensating for the degradation defects of traditional epoxy-isocyanate systems under excessive sulfur conditions.

[0009] This invention, by introducing trace amounts of active sulfur-containing compounds and combining them with a designed formulation, significantly reduces the proportion of the two main expensive components—epoxy compounds and blocked isocyanate compounds—in the first bath impregnation solution without weakening adhesive performance. This allows the solid content of the first bath impregnation solution to be reduced from the conventional 3.00–6.50% to a lower level (e.g., 2.30–2.80%), achieving the dual goals of improved performance and significant cost savings on raw materials. It not only expands the application scenarios of active sulfur-containing compounds from high-solids-content systems to low-solids-content first bath impregnation solutions but also enhances interfacial durability through chemical crosslinking. This provides a more economical, environmentally friendly, and reliable solution for fiber-reinforced material impregnation technology, demonstrating strong practical value and promising prospects for widespread application.

[0010] Preferably, the solid content of the first bath impregnation solution is 2.00~3.50%.

[0011] As a further preferred embodiment, the solid content of the first bath impregnation solution is 2.00~2.80%.

[0012] As a further preferred embodiment, the solid content of the first bath impregnation solution is 2.30~2.80%.

[0013] By controlling the solid content of the first bath impregnation solution at 2.30~2.80%, the active components can be effectively impregnated into the fibers, while avoiding problems such as increased viscosity and cost caused by excessive solid content. This approach is conducive to promoting its application in industrial production.

[0014] Preferably, the weight of the active sulfur-containing compound is 1.00 to 3.00% of the dry weight of the first bath impregnation solution.

[0015] As a further preferred embodiment, the dry weight of the first bath impregnation solution, by weight, comprises: 68-80 parts of blocked isocyanate compounds, 18-30 parts of epoxy compounds, and 1-5 parts of active sulfur-containing compounds.

[0016] As a further preferred embodiment, the dry weight of the first bath impregnation solution includes 1.5 to 3 parts by weight of an active sulfur-containing compound.

[0017] Preferably, the active sulfur-containing compound includes a disulfide bond, a trisulfide bond, or a tetrasulfide bond, and contains at least one second functional group, wherein the second functional group is any one or a combination of two of siloxane, alkoxysilyl, carboxyl, hydroxyl, amino, and epoxy groups.

[0018] This invention introduces a structurally unique active sulfur-containing compound into the first bath impregnation solution based on epoxy compounds and blocked isocyanate compounds. The active sulfur-containing compound possesses two key functional groups: first, a sulfur bond functional group, namely disulfide, trisulfide, or tetrasulfide bonds in the molecule. These polysulfide bonds can break during rubber vulcanization and participate in the formation of covalent crosslinks with the unsaturated chains of the rubber, thereby establishing a direct chemical connection between the impregnation layer and the rubber components; second, a secondary functional group, namely active groups such as siloxane, alkoxysilyl, carboxyl, hydroxyl, amino, and epoxy groups simultaneously contained in the molecule. This invention utilizes the secondary functional group to chemically react (e.g., ring-opening reactions, substitution reactions, etc.) with the main components of the first bath impregnation solution (epoxy compounds and / or blocked isocyanate compounds) during the heat treatment (drying and curing) after impregnation, thereby covalently anchoring the entire active sulfur-containing compound molecule to the crosslinked network framework formed by the first bath impregnation solution. This design transforms the active sulfur-containing compound from a simple, physically doped additive that is easily migrated or lost into an integral part of the impregnation layer network structure, with its terminal sulfur bonds facing outwards, preparing it for subsequent bonding with rubber components.

[0019] Preferably, the structure of the active sulfur-containing compound is shown in general formula I: ; General Formula I; Where a is an integer from 1 to 3; p and q are each an integer from 0 to 3, and p and q are not both 0 at the same time; K1 and K2 are each independently unsubstituted or branched C1~C1. 10 Alkyl chain, C1~C 10 alkenyl chain, C1~C 10 alkynyl chain, C1~C 10 Heterochain, C3~C 10 cycloalkyl chain, C2~C 10 Cyclic heterochain, C3~C 10 Cyclic double-bonded chain, C3~C 10 Cyclic compounds containing any one or more of the following: triple-bonded chains, phenyl groups, naphthyl groups, and heterocyclic groups; The heterochain is a carbon chain containing any one or more combinations of oxygen, nitrogen, and sulfur atoms; The heterocyclic group is any one or a combination of pyridine, thiophene, and furan; The branched chain includes any one or more combinations of alkyl chain, alkenyl chain, alkynyl chain, heterochain, cycloalkyl chain, cyclic heterochain, cyclic chain containing double bond, cyclic chain containing triple bond, phenyl, naphthyl, and heterocyclic group; R1 and R2 are each independently C3~C 12 It is any one or more combinations of alkoxysilyl, carboxyl, hydroxyl, amino, or epoxy groups.

[0020] Preferably, when R1 or R2 is trialkoxysilyl or dialkoxymethylsilyl, the number of carbon atoms in K1 or K2 does not exceed 4; When R1 or R2 is an epoxy group, the total number of carbon atoms in K1 or K2 does not exceed 3; When R1 or R2 is a carboxyl group, the total number of carbon atoms in K1 or K2 is no more than 6 times the number of carbon atoms in the carboxyl group; When R1 or R2 is an amino group, the total number of carbon atoms in K1 or K2 is no more than 4 times the number of amino groups; When R1 or R2 is a hydroxyl group, the total number of carbon atoms in K1 or K2 is no more than 4 times the number of oxygen atoms.

[0021] As a preferred option When R1 and R2 are combinations of two or more of the following groups: carboxyl, hydroxyl, and amino, the total number of carbon atoms C in K1 or K2 must satisfy the following: C≤4+6*n c +4*n h +4*n a ; Where, n c n represents the number of carboxyl groups. h n represents the number of hydroxyl groups. a n represents the number of amino groups.c + n h + n a ≥2.

[0022] Preferably, when R1 and R2 are combinations of two or more of carboxyl, hydroxyl, and amino groups, p or q ≥ 2 in general formula I, and the two second functional groups located on the same side of the sulfur atom are located on two carbon atoms respectively.

[0023] Preferably, in general formula I, a=1, p=1 or 2, q=1 or 2, and K1 or K2 are each independently a C1 to C3 alkylene group.

[0024] This invention, for the first time, incorporates an active sulfur-containing compound into the first bath of a two-bath impregnation process, forming a "polysulfide bond-KR" structure, which significantly improves the adhesive properties and over-sulfur degradation performance of the impregnated rubber. The common structural feature of active sulfur-containing compounds is that the polysulfide bonds participate in the vulcanization of the latex / rubber components. K represents the linking group (i.e., the carbon chain portion of the compound, exhibiting chemical inertness, but its solubility, dispersibility, and non-volatility in the impregnation often depend on the number of carbon atoms and the structure). R represents the active group, responsible for providing cross-linking reactivity between the additive molecules and the impregnated rubber (epoxy-isocyanate system). Mechanistically, after the first bath impregnation, a cross-linking reaction occurs during heating in the oven. The R group participates in the epoxy-isocyanate reaction, cross-linking the active sulfur-containing compound molecules to the network structure of the impregnated rubber. The polysulfide bonds then interact with the disulfide bond system of the latex or rubber in the second bath during the second bath impregnation and tire vulcanization process, forming chemical bonds with the rubber molecules.

[0025] Preferably, the active sulfur-containing compound is any one or a combination of cystamine dihydrochloride, 3,3-dithiodipropionic acid, bis[3-(triethoxysilyl)propyl]-disulfide, bis(2-epoxypropyl)disulfide, bis(3-hydroxypropyl)disulfide, bis[3-(triethoxysilyl)propyl]-tetrasulfide, cystine, and bis(2,3-dihydroxypropyl)disulfide.

[0026] Preferably, the epoxy compound includes at least one epoxy monomer, the epoxy monomer contains at least one epoxy group, and the epoxy monomer is a water-soluble or water-dispersible compound.

[0027] As a further preferred embodiment, the epoxy compound is any one or a combination of glycidyl ether resins, phenolic glycidyl ether resins, epoxidized linear phenolic resins, glycidyl ester resins, glycidyl amine resins, epoxidized olefin resins with hydrophilic groups, and glycidyl.

[0028] As a further preferred embodiment, the epoxy compound includes monoglycidyl ethers or polyglycidyl ethers containing any one or more combinations of ethylene glycol, propylene glycol, butanediol, glycerol, 2-hydroxymethyl-1,3-propanediol, trimethylolethane, pentaerythritol, sorbitol, and xylitol.

[0029] As a further preferred embodiment, the epoxy compound further includes glycidyl ether, diglycidyl ether, glycidyl methyl ether and / or glycidyl ethyl ether.

[0030] Preferably, the blocked isocyanate compound is an isocyanate protected by a blocking agent; The blocking agents include: alcohols, phenols, β-dicarbonyl compounds, oxime compounds and / or amide compounds; The isocyanate is any one or a combination of diphenylmethane-4,4'-diisocyanate (MDI), toluene diisocyanate (TDI), polymethylene polyphenyl polyisocyanate (PAPI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), 1,6-hexanediisocyanate (HDI), isophorone diisocyanate (IPDI), and terephthalic diisocyanate (PPDI).

[0031] As a further preferred embodiment, the isocyanate is any one or a combination of terephthalic diisocyanate (PPDI), toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), and 1,6-hexamethylene diisocyanate (HDI).

[0032] Preferably, the dry weight of the first bath impregnation solution also includes 0 to 15 parts of additives.

[0033] As a further preferred embodiment, the additives include any one or more combinations of dispersants, viscosity modifiers (thickeners), wetting and penetrating agents, defoamers, pH adjusters, surfactants, film-forming agents, antioxidants, and / or crosslinking catalysts.

[0034] The method for preparing the first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, as described above, includes the following steps: Add each raw material to water according to the formula ratio and mix evenly to obtain the first bath impregnation solution.

[0035] As a further preferred option, the active sulfur-containing compound can be added to the preparation solution at any step of the preparation process and mixed evenly by thorough stirring.

[0036] As a further preferred option, the active sulfur-containing compound is added directly to the water, followed by the addition of an epoxy compound and a blocked isocyanate compound.

[0037] As a further preferred option, epoxy compounds are first added to water, followed by active sulfur-containing compounds, and finally blocked isocyanate compounds are added.

[0038] As a further preferred option, an aqueous solution of an epoxy compound and a blocked isocyanate compound is first prepared, and then an active sulfur-containing compound is added.

[0039] As a further preferred embodiment, the active sulfur-containing compound is the active sulfur-containing compound itself or a dispersion of the active sulfur-containing compound.

[0040] As a further preferred embodiment, the dispersion of the active sulfur-containing compound is prepared by diluting the active sulfur-containing compound by 0.5 to 20 times using an amphiphilic solvent.

[0041] As a further preferred embodiment, the amphiphilic solvent is any one or a combination of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, butanediol, tetrahydrofuran, and acetone.

[0042] As a further preferred option, an acid or alkali is used to react the ionizable amine or carboxyl groups in the active sulfur-containing compound to generate an ammonium salt or carboxylate solution of the active sulfur-containing compound, and this ammonium salt or carboxylate solution of the active sulfur-containing compound is added to the first bath impregnation system of the two-bath impregnation method for fiber skeleton materials in any step of the preparation process.

[0043] As a further preferred option, the active sulfur-containing compound is thoroughly mixed with the blocked isocyanate compound or epoxy compound without the presence of any additives or with the addition of a dispersant, and then dispersed using the blocked isocyanate mother liquor containing the active sulfur-containing compound or the epoxy compound mother liquor containing the active sulfur-containing compound.

[0044] As a further preferred embodiment, the dispersant is any one or a combination of amphiphilic solvents, acids, and bases.

[0045] Therefore, the present invention has the following beneficial effects: (1) For the first time, this invention adds an active sulfur-containing compound to the first bath of the two-bath impregnation method to form a "polysulfide bond-KR" structure, which is equivalent to providing a clear chemical crosslink between the first bath impregnation and the second bath / rubber, thereby improving the vulcanization peel force and the adhesive performance and over-sulfurization degradation performance of the impregnation. (2) The first bath impregnation solution of the present invention effectively improves the bonding strength between the skeleton material and the rubber in the vulcanized and over-vulcanized state, and reduces the risk of cord delamination in the tire; (3) The active sulfur-containing compound provided by the present invention has a simple structure, is inexpensive and readily available, and does not require refining or purification. The crude product can be directly used in the preparation of the impregnation solution, which is highly economical. In the first bath impregnation solution, compared with the additives with more functional groups (epoxy, etc.) and complex structures in the prior art, the addition of the active sulfur-containing compound has a significant cost advantage; (4) By introducing a trace amount of active sulfur-containing compound into the first bath impregnation solution, the present invention can significantly reduce the amount of the two main components, epoxy compounds and blocked isocyanates, in the first bath impregnation solution while ensuring the initial vulcanization and over-sulfurization performance of the impregnation. The solid content can be reduced from the conventional 3.00~6.50% to 2.30~2.80%, which significantly saves raw material costs while improving the adhesive performance of the impregnation. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0047] The reaction raw materials used in the following examples and comparative examples are as follows: 1. Cystamine dihydrochloride (analytical grade), purchased from Titan Science Exploration Platform, denoted as S1, has the following structural formula (1): ; Equation (1).

[0048] 2,3,3-Dithiodipropionic acid (analytical grade), purchased from Titan Science and Technology Exploration Platform, denoted as S2, has the following structural formula (2): ; Equation (2).

[0049] 3. Bis[3-(triethoxysilyl)propyl]-disulfide (analytical grade), purchased from Titan Technology Exploration Platform, denoted as S3, has the following structural formula (3): ; Equation (3).

[0050] 4. Bis[2-epoxypropyl]-disulfide (EC3-D), self-made, denoted as S4, its structural formula is shown in formula (4) below: ; Equation (4).

[0051] 5. Bis[3-hydroxypropyl]-disulfide (HC3-D), self-made, denoted as S5, has the following structural formula (5): ; Equation (5).

[0052] 6. Bis[3-(triethoxysilyl)propyl]-tetrasulfide (analytical grade), purchased from Titan Technology Exploration Platform, denoted as S6, has the following structural formula (6): ; Equation (6).

[0053] 7. Cystine (analytical grade), purchased from Titan Science Exploration Platform, designated as S7, has the following structural formula (7): ; Equation (7).

[0054] 8. Bis[2,3-dihydroxypropyl]-disulfide (H2C3-D), self-made, denoted as S8, has the following structural formula (8): ; Equation (8).

[0055] The aforementioned self-made compounds were all prepared by substitution reaction of the corresponding chlorinated precursors (epoxychloropropane / 3-chloro-1-propanol / 3-chloro-1,2-propanediol) with sodium disulfide aqueous solution. This reaction is a well-known organic chemical reaction in the industry and has been reported and disclosed in literature and patents, so it will not be described in detail here.

[0056] The epoxy compound used is ethylene glycol diglycidyl ether, purchased from Titan Technology Exploration Platform, with a nominal epoxy value of 0.7. The 50% blocked isocyanate emulsion is caprolactam-blocked terephthalic diisocyanate (a 50% solids aqueous dispersion, sourced from the company's internal tire cord impregnation production line).

[0057] Example 1: This embodiment provides a first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials and its preparation method.

[0058] A first bath impregnation solution for a two-bath impregnation method for fiber-reinforced materials comprises: 3.73 g of epoxy compounds; the epoxy compound was ethylene glycol diglycidyl ether. 20.52 g of 50% blocked isocyanate emulsion; the 50% blocked isocyanate emulsion is caprolactam-blocked terephthalic diisocyanate (50% aqueous dispersion); 0.28 g of the active sulfur-containing compound; the active sulfur-containing compound is S1 as described above; 375.47 g of deionized water.

[0059] The total weight of the first bath impregnation solution is 400 g, its solid content is 3.50%, and the mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution.

[0060] A method for preparing the first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials includes the following steps: The raw materials described above are added to deionized water according to the formula ratio and mixed evenly to obtain the first bath impregnation solution.

[0061] As one implementation method, the active sulfur-containing compound can be added to the preparation solution at any step of the preparation process and homogenized by thorough stirring. Specifically, the active sulfur-containing compound can be added directly to water, followed by the epoxy compound and the blocked isocyanate compound. Alternatively, the epoxy compound can be added to water first, followed by the active sulfur-containing compound, and finally the blocked isocyanate compound. Another method is to first prepare an aqueous solution of the epoxy compound and the blocked isocyanate compound, and then add the active sulfur-containing compound.

[0062] As one implementation method, the active sulfur-containing compound can be added directly in its bulk form, or it can be diluted 0.5 to 20 times with an amphiphilic solvent to obtain a solution (i.e., a dispersion of the active sulfur-containing compound) before addition. The amphiphilic solvent can be one or more of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, butanediol, tetrahydrofuran, and acetone.

[0063] In one implementation, the first bath impregnation solution can be reacted with an acid or alkali to the ionizable amine or carboxyl groups in the active sulfur-containing compound, generating an ammonium salt or carboxylate solution of the active sulfur-containing compound. This ammonium salt or carboxylate solution is then added to the first bath impregnation solution system in the two-bath impregnation method for fiber skeleton materials at any step of the preparation process. If a suitable pH value is required for the first bath impregnation solution, the pH of the prepared mixture can be adjusted to an appropriate value after the ammonium salt or carboxylate solution of the active sulfur-containing compound is added to the first bath impregnation solution.

[0064] In one embodiment, the active sulfur-containing compound is thoroughly mixed with the blocked isocyanate compound or epoxy compound raw material without the presence of any additives or with the addition of a dispersant (amphiphilic solvent, acid, or base), and then dispersed using the blocked isocyanate mother liquor or epoxy compound mother liquor containing the active sulfur-containing compound.

[0065] This embodiment also provides a second impregnation solution for a two-bath impregnation method for fiber skeleton materials.

[0066] The second bath impregnation solution used in the two-bath impregnation process for fiber-reinforced materials uses latex produced by the company, and has the following formula: The mixture consisted of 84 parts pure water, 3.4 parts resorcinol, 7.2 parts formaldehyde (37% formalin aqueous solution), 75 parts 40% butadiene-pyridine latex, and 5.6 parts 10% sodium hydroxide solution. The pH of the second bath impregnation solution was 9.4.

[0067] This embodiment also provides a single-line impregnation method.

[0068] The single-line impregnation process uses 1000D / 2, 450T / m conventional polyester cord, and the cord surface has not undergone any special activation or washing treatment. The winding direction, temperature, and residence time on the machine are as follows: unwinding roller - first bath impregnation tank (room temperature, 5 s) - first bath first oven (170 ℃, 4 min), first bath second oven (240 ℃, 4 min) - second bath impregnation tank (room temperature, 5 s) - second bath first oven (170 ℃, 4 min) - second bath second oven (240 ℃, 4 min) - softener - take-up roller. The take-up tension is maintained at 5 N by a tension adjustment device to obtain the impregnated cord.

[0069] The adhesive performance of the cords was evaluated using the CRA peel test, as specified in GB / T40725-2021, which describes the test performance of adhesive-impregnated cords to rubber. Bridgestone-supplied test rubber was used. Six groups of cord samples (seven cords per group) were wound onto a mold, covered with rubber, and then vulcanized at 160 °C and a clamping pressure of 2.45 MPa for 20 min (normal vulcanization) or 60 min (over-vulcanization). The middle five cords of each group were then fixed to one clamp of the tensile testing machine, while the rubber was fixed to the other clamp. The cords were peeled from the surface of the test rubber by tension between the clamps. The force required to peel the cords from the rubber (CRA peel force, unit: Newtons / N) was measured, and the rubber coverage on the peeled surface was observed and rated (A being the best, E the worst). It should be noted that CRA testing is affected by factors such as the quality of rubber compounding, additive precipitation during storage, pre-drying degree, and cord moisture regain; cord impregnation is also affected by multiple factors such as fluctuations in the oil content of the single cord, the ambient temperature and humidity of the single cord impregnation machine, and the repeatability of oven temperature control. Therefore, while using active sulfur compounds for impregnation, the impregnation formulation in the comparative example below is also used for single cord impregnation experiments. Then, during vulcanization / over-vulcanization testing, the same test rubber sheet is used for both vulcanization and over-vulcanization tests and comparisons. Therefore, the peel strength and peel surface rating in each example are compared with the results of the corresponding comparative example in that example (only the formulation of the first bath impregnation solution used in the two-bath impregnation method for fiber skeleton materials in the comparative example used to form the control group is the same as the formulation in the comparative example below). The examples are not compared with each other using absolute values.

[0070] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 71.26 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 63.40 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 59.42 N, and the peel surface rating was C; in the same group, the peel force of control example 1 was 54.28 N, and the peel surface rating was C.

[0071] Example 2 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.07 g; the active sulfur-containing compound is S3 as described above; and deionized water is 375.68 g. The mass of the active sulfur-containing compound contained in the first bath impregnation solution accounts for 0.50% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0072] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 74.32 N, and the peel surface rating was A; in the same group, the peel force of control example 1 (solid content 3.50%) was 64.78 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 80.94 N, and the peel surface rating was B; in the same group, the peel force of control example 1 was 79.15 N, and the peel surface rating was B.

[0073] Example 3 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.14 g; the active sulfur-containing compound is S3 as described above; and the deionized water is 375.61 g. The mass of the active sulfur-containing compound contained in the first bath impregnation solution accounts for 1.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0074] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 80.59 N, and the peel surface rating was B; in the same control example 1 (solid content 3.50%), the peel force was 63.00 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 88.57 N, and the peel surface rating was A; in the same control example 1, the peel force was 76.05 N, and the peel surface rating was B.

[0075] Example 4 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.21 g; the active sulfur-containing compound is S3 as described above; and the deionized water is 375.54 g. The mass of the active sulfur-containing compound contained in the first bath impregnation solution accounts for 1.50% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0076] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 96.15 N, and the peel surface rating was A; in the same group, the peel force of control example 1 (solid content 3.50%) was 86.80 N, and the peel surface rating was A. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 85.65 N, and the peel surface rating was B; in the same group, the peel force of control example 1 was 73.93 N, and the peel surface rating was B.

[0077] Example 5 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is 0.28 g; the active sulfur-containing compound is S3 as described above; and the deionized water is 375.47 g. Everything else is the same as in Example 1.

[0078] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 97.21 N, and the peel surface rating was A; in the same control example 1 (solid content 3.50%), the peel force was 86.80 N, and the peel surface rating was A. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 96.62 N, and the peel surface rating was B; in the same control example 1, the peel force was 73.93 N, and the peel surface rating was B.

[0079] Example 6 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.35 g; the active sulfur-containing compound is S3 as described above; and the deionized water is 375.40 g. The active sulfur-containing compound contained in the first bath impregnation solution accounts for 2.50% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0080] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 97.51 N, and the peel surface rating was A; in the same group, the peel force of control example 1 (solid content 3.50%) was 88.15 N, and the peel surface rating was A. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 91.58 N, and the peel surface rating was A; in the same group, the peel force of control example 1 was 71.63 N, and the peel surface rating was A.

[0081] Example 7 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.42 g; the active sulfur-containing compound is S3 as described above; and the deionized water is 375.33 g. The mass of the active sulfur-containing compound contained in the first bath impregnation solution accounts for 3.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0082] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 87.38 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 84.25 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 86.74 N, and the peel surface rating was B; in the same group, the peel force of control example 1 was 75.32 N, and the peel surface rating was B.

[0083] Example 8 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.70 g; the active sulfur-containing compound is S3 as described above; and deionized water is 375.05 g. The active sulfur-containing compound contained in the first bath impregnation solution accounts for 5.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0084] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 87.90 N, and the peel surface rating was B; in the same control example 1 (solid content 3.50%), the peel force was 84.07 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 80.62 N, and the peel surface rating was B; in the same control example 1, the peel force was 75.92 N, and the peel surface rating was B.

[0085] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation process of fiber skeleton materials, wherein no active sulfur-containing compounds are added; the amount of deionized water is 375.75 g. Everything else is the same as in Example 1.

[0086] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is 0.04 g; the active sulfur-containing compound is S3 as described above; and deionized water is 375.71 g. The active sulfur-containing compound contained in the first bath impregnation solution accounts for 0.25% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0087] The results of the 20-minute CRA vulcanization test are as follows: In this comparative example, the peel force was 77.06 N, and the peel surface rating was B; in the same group, the peel force of comparative example 1 (solid content 3.50%) was 82.73 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this comparative example, the peel force was 75.08 N, and the peel surface rating was B; in the same group, the peel force of comparative example 1 was 80.26 N, and the peel surface rating was B.

[0088] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, wherein the active sulfur-containing compound is 0.77 g; the active sulfur-containing compound is S3 as described above; and the deionized water is 374.98 g. The active sulfur-containing compound contained in the first bath impregnation solution accounts for 5.50% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0089] The results of the 20-minute CRA vulcanization test are as follows: In this comparative example, the peel force was 67.85 N, and the peel surface rating was B; in the same group, the peel force of comparative example 1 (solid content 3.50%) was 67.39 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this comparative example, the peel force was 81.88 N, and the peel surface rating was B; in the same group, the peel force of comparative example 1 was 83.85 N, and the peel surface rating was B.

[0090] Impregnated cords were prepared according to the methods described in Examples 1-8 and Comparative Examples 1-3, and CRA vulcanization tests were performed on them respectively. The test methods are the same as those described above and will not be repeated here. The composition of the first bath impregnation solution with different concentrations of active sulfur-containing compounds is shown in Table 1 below.

[0091] Table 1: Epoxy compounds (g) 3.73 3.73 3.73 3.73 3.73 3.73 3.73 3.73 3.73 3.73 3.73 50% blocked isocyanate emulsion (g) 20.52 20.52 20.52 20.52 20.52 20.52 20.52 20.52 20.52 20.52 20.52 Deionized water (g) 375.47 375.68 375.61 375.54 375.47 375.40 375.33 375.05 375.75 375.71 374.98 Added active sulfur-containing compounds S1 S3 S3 S3 S3 S3 S3 S3 / S3 S3 Weight (g) of the active sulfur-containing compound or its dispersion added. 0.28 0.07 0.14 0.21 0.28 0.35 0.42 0.70 / 0.04 0.77 Total weight (g) 400 400 400 400 400 400 400 400 400 400 400 Solid content (%) 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 Weight percentage of active sulfur-containing compounds (as a percentage of dry weight) (%) 2.00 0.50 1.00 1.50 2.00 2.50 3.00 5.00 / 0.25 5.50 .

[0092] Analysis of the peel force data corresponding to the formulations in Table 1 shows that, based on Example 5, changing the amount of active sulfur-containing compound added, as shown in Examples 2-8 of Table 1 (0.50%, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%, and 5.00% of dry weight respectively), and the adhesive performance results after 20 or 60 min of vulcanization, indicates that when the addition amount is 0.50% and 5.00%, compared with the same group as Comparative Example 1, 5.00% slightly improves the adhesive performance more than 0.50%, but there is no significant difference. However, further increasing to 5.50% leads to a significant decrease in adhesive performance. Therefore, excessive addition of active sulfur-containing compounds may cause a shift in the functional group ratio of the epoxy-isocyanate system and may competitively react with the polyester end groups, resulting in insufficient activation of the polyester surface, thus leading to a decrease in adhesive performance. Therefore, the preferred addition amount of active sulfur-containing compounds is 0.50-5.00% of dry weight.

[0093] Example 9 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: epoxy compound is 2.98 g; 50% blocked isocyanate emulsion is 16.42 g; active sulfur-containing compound is 0.22 g of the above-mentioned S2; and deionized water is 380.38 g.

[0094] The first bath impregnation solution has a solid content of 2.80%, and the mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0095] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 87.92 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (3.50% solid content) was 86.77 N, and the peel surface rating was B; in the same group, the peel force of control example 9 (2.90% solid content) was 73.05 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 90.09 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (3.50% solid content) was 73.37 N, and the peel surface rating was B; in the same group, the peel force of control example 9 (2.90% solid content) was 60.19 N, and the peel surface rating was B.

[0096] Example 10 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: 2.47 g of epoxy compound; 13.50 g of 50% blocked isocyanate emulsion; 0.18 g of the above-mentioned S2 of active sulfur compound; and 383.85 g of deionized water.

[0097] The first bath impregnation solution has a solid content of 2.30%, and the active sulfur-containing compounds it contains account for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0098] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 87.83 N, and the peel surface rating was B; the peel force in the same group control example 1 (3.50% solid content) was 85.68 N, and the peel surface rating was B; the peel force in the same group control example 5 (2.30% solid content) was 70.77 N, and the peel surface rating was B; the peel force in the same group control example 6 (2.50% solid content) was 75.43 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 87.99 N, and the peel surface rating was B; the peel force in the same group control example 1 (3.50% solid content) was 72.65 N, and the peel surface rating was B; the peel force in the same group control example 5 (2.30% solid content) was 53.72 N, and the peel surface rating was C; the peel force in the same group control example 6 (2.50% solid content) was 71.81 N, and the peel surface rating was C.

[0099] Example 11 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: epoxy compound is 2.98 g; 50% blocked isocyanate emulsion is 16.42 g; active sulfur-containing compound is 0.22 g of the above-mentioned S3; and deionized water is 380.38 g.

[0100] The first bath impregnation solution has a solid content of 2.80%, and the mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0101] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 78.09 N, and the peel surface rating was B; the peel force in the same control example 1 (3.50% solid content) was 77.22 N, and the peel surface rating was B; the peel force in the same control example 4 (2.80% solid content) was 68.14 N, and the peel surface rating was B; the peel force in the same control example 9 (2.90% solid content) was 67.63 N, and the peel surface rating was C. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 88.84 N, and the peel surface rating was B; the peel force in the same control example 1 (3.50% solid content) was 72.62 N, and the peel surface rating was B; the peel force in the same control example 4 (2.80% solid content) was 72.25 N, and the peel surface rating was B; the peel force in the same control example 9 (2.90% solid content) was 67.35 N, and the peel surface rating was C.

[0102] Example 12 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: 2.47 g of epoxy compound; 13.50 g of 50% blocked isocyanate emulsion; 0.18 g of the above-mentioned S3 of active sulfur compound; and 383.85 g of deionized water.

[0103] The first bath impregnation solution has a solid content of 2.30%, and the active sulfur-containing compounds it contains account for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0104] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 75.89 N, and the peel surface rating was B; the peel force in the same group control example 1 (3.50% solid content) was 72.46 N, and the peel surface rating was B; the peel force in the same group control example 5 (2.30% solid content) was 68.48 N, and the peel surface rating was B; the peel force in the same group control example 6 (2.50% solid content) was 71.79 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 83.68 N, and the peel surface rating was B; the peel force in the same group control example 1 (3.50% solid content) was 72.23 N, and the peel surface rating was B; the peel force in the same group control example 5 (2.30% solid content) was 68.64 N, and the peel surface rating was B; the peel force in the same group control example 6 (2.50% solid content) was 71.64 N, and the peel surface rating was C.

[0105] Example 13 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: epoxy compound is 1.07 g; 50% blocked isocyanate emulsion is 5.87 g; active sulfur compound is 0.07 g; active sulfur compound is S3 as described above; and deionized water is 392.99 g.

[0106] The total weight of the first bath impregnation solution is 400 g, its solid content is 1.00%, and the mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0107] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 73.91 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 68.17 N, and the peel surface rating was B; in the same group, the peel force of control example 8 (solid content 1.80%) was 49.63 N, and the peel surface rating was C. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 79.54 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 68.16 N, and the peel surface rating was B; in the same group, the peel force of control example 8 (solid content 1.80%) was 32.98 N, and the peel surface rating was C.

[0108] Example 14 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: epoxy compound is 2.13 g; 50% blocked isocyanate emulsion is 11.73 g; active sulfur compound is 0.25 g; active sulfur compound is S3 as described above; and deionized water is 385.89 g.

[0109] The total weight of the first bath impregnation solution is 400 g, its solid content is 2.00%, and the mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0110] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 77.49 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (3.50% solid content) was 62.20 N, and the peel surface rating was C; in the same group, the peel force of control example 5 (2.30% solid content) was 55.97 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 86.24 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (3.50% solid content) was 69.54 N, and the peel surface rating was B; in the same group, the peel force of control example 5 (2.30% solid content) was 34.46 N, and the peel surface rating was C.

[0111] Example 15 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein: epoxy compound is 5.33 g; 50% blocked isocyanate emulsion is 29.33 g; active sulfur compound is 0.35 g; active sulfur compound is S3 as described above; and deionized water is 364.99 g.

[0112] The total weight of the first bath impregnation solution is 400 g, its solid content is 5.00%, and the mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0113] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 91.21 N, and the peel surface rating was A; the peel force in the same group control example 1 (3.50% solid content) was 70.78 N, and the peel surface rating was B; the peel force in the same group control example 7 (5.50% solid content) was 77.69 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 88.60 N, and the peel surface rating was B; the peel force in the same group control example 1 (3.50% solid content) was 83.39 N, and the peel surface rating was B; the peel force in the same group control example 7 (5.50% solid content) was 51.03 N, and the peel surface rating was C.

[0114] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation process of fiber skeleton materials, wherein no active sulfur-containing compounds are added; 2.99 g of epoxy compound; 16.43 g of 50% blocked isocyanate emulsion; and 380.58 g of deionized water. The solid content of the first bath impregnation solution is 2.80%, and all other components are the same as in Example 1.

[0115] Comparative Example 5 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation process of fiber skeleton materials, wherein no active sulfur-containing compounds are added; the epoxy compound is 2.46 g; the 50% blocked isocyanate emulsion is 13.51 g; and the deionized water is 384.03 g. The solid content of the first bath impregnation solution is 2.30%, and all other contents are the same as in Example 1.

[0116] Comparative Example 6 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein no active sulfur-containing compounds are added; 2.66 g of epoxy compounds; 14.67 g of 50% blocked isocyanate emulsion; and 382.67 g of deionized water.

[0117] The total weight of the first bath impregnation solution was 400 g, and its solid content was 2.50%. Everything else was the same as in Example 1.

[0118] Comparative Example 7 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein no active sulfur-containing compounds are added; 5.87 g of epoxy compounds; 32.27 g of 50% blocked isocyanate emulsion; and 361.86 g of deionized water.

[0119] The total weight of the first bath impregnation solution was 400 g, and its solid content was 5.50%. Everything else was the same as in Example 1.

[0120] Comparative Example 8 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein no active sulfur-containing compounds are added; 1.92 g of epoxy compounds; 10.56 g of 50% blocked isocyanate emulsion; and 387.52 g of deionized water.

[0121] The total weight of the first bath impregnation solution was 400 g, and its solid content was 1.80%. Everything else was the same as in Example 1.

[0122] Comparative Example 9 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein no active sulfur-containing compounds are added; 3.09 g of epoxy compounds; 17.01 g of 50% blocked isocyanate emulsion; and 379.90 g of deionized water.

[0123] The total weight of the first bath impregnation solution was 400 g, and its solid content was 2.90%. Everything else was the same as in Example 1.

[0124] Comparative Example 10 The difference between this comparative example and Example 1 is as follows: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein 0.04 g of the above-mentioned active sulfur-containing compound S3 is added; 0.53 g of epoxy compound; 2.93 g of 50% blocked isocyanate emulsion; and 396.50 g of deionized water.

[0125] The total weight of the first bath impregnation solution is 400 g, and its solid content is 0.50%. The mass of the active sulfur-containing compounds it contains accounts for 2.00% of the dry weight of the first bath impregnation solution. Everything else is the same as in Example 1.

[0126] The 20-minute CRA vulcanization test results are as follows: In this comparative example, the peel force was 51.65 N, and the peel surface rating was B; in the same group, the control example 8 (1.80% solid content) had a peel force of 43.82 N, and the peel surface rating was B. The 60-minute CRA over-vulcanization test results are as follows: In this comparative example, the peel force was 52.39 N, and the peel surface rating was B; in the same group, the control example 8 (1.80% solid content) had a peel force of 42.48 N, and the peel surface rating was C.

[0127] Cords were prepared according to the methods described in Examples 9-15, Comparative Examples 1, and Comparative Examples 4-10, and CRA vulcanization tests were performed on them respectively. The test methods were the same as those described above and will not be repeated here. The composition of the first bath impregnation solution with different solid contents is shown in Table 2 below.

[0128] Table 2: Example 9 2.98 16.42 380.38 S2 0.22 400 2.80 2.00 Example 10 2.47 13.50 383.85 S2 0.18 400 2.30 2.00 Example 11 2.98 16.42 380.38 S3 0.22 400 2.80 2.00 Example 12 2.47 13.50 383.85 S3 0.18 400 2.30 2.00 Example 13 1.07 5.87 392.99 S3 0.07 400 1.00 2.00 Example 14 2.13 11.73 385.89 S3 0.25 400 2.00 2.00 Example 15 5.33 29.33 364.99 S3 0.35 400 5.00 2.00 Comparative Example 1 3.73 20.52 375.75 / / 400 3.50 / Comparative Example 4 2.99 16.43 380.58 / / 400 2.80 / Comparative Example 5 2.46 13.51 384.03 / / 400 2.30 / Comparative Example 6 2.66 14.67 382.67 / / 400 2.50 / Comparative Example 7 5.87 32.27 361.86 / / 400 5.50 / Comparative Example 8 1.92 10.56 387.52 / / 400 1.80 / Comparative Example 9 3.09 17.01 379.90 / / 400 2.90 / Comparative Example 10 0.53 2.93 396.50 S3 0.04 400 0.50 2.00 .

[0129] Data analysis of the peel strength corresponding to the formulations in Table 2: Comparative examples 9-12 and comparative examples 4-6 show that when the solid content is reduced to 2.30% and 2.80%, respectively, the adhesive performance of the prepared impregnated cords does not decrease significantly. However, at the same solid content, the peel strength of the cords in the comparative examples without the addition of active sulfur compounds is significantly lower. Comparative examples 13-15 and comparative examples 7-9 show that even with the addition of active sulfur compound S3 at a low solid content of 1.00%-2.00%, the addition of the two main components, epoxy compounds and blocked isocyanates, in the first bath impregnation solution can be significantly reduced while ensuring the initial vulcanization and over-sulfur adhesive strength of the impregnation. In addition, comparative examples 8 and 10 show that at a solid content of 0.50%, even with the addition of active sulfur compounds, the peel strength is still low and cannot bring the peel performance to an acceptable range. This indicates that even in the presence of active sulfur compounds, there is a lower limit to the reduction of the solid content of the first bath impregnation solution. Therefore, the over-sulfurization peeling force of the present invention with the addition of active sulfur-containing compounds at low solid content is significantly higher than that of the comparative example with higher solid content. It can reduce solid content while ensuring peeling force, thereby significantly reducing production costs.

[0130] Example 16 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S2 as described above. Everything else is the same as in Example 1.

[0131] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 73.05 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 70.77 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 60.19 N, and the peel surface rating was C; in the same group, the peel force of control example 1 was 53.72 N, and the peel surface rating was C.

[0132] Example 17 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S3 as described above. Everything else is the same as in Example 1.

[0133] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 91.11 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 86.77 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 86.13 N, and the peel surface rating was A; in the same group, the peel force of control example 1 was 76.72 N, and the peel surface rating was B.

[0134] Example 18 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S4 as described above. Everything else is the same as in Example 1.

[0135] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 78.28 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 77.46 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 70.38 N, and the peel surface rating was B; in the same group, the peel force of control example 1 was 69.24 N, and the peel surface rating was C.

[0136] Example 19 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S5 as described above. Everything else is the same as in Example 1.

[0137] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 77.64 N, and the peel surface rating was B; in the same control example 1 (solid content 3.50%), the peel force was 76.98 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 72.34 N, and the peel surface rating was B; in the same control example 1, the peel force was 69.37 N, and the peel surface rating was C.

[0138] Example 20 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S6 as described above. Everything else is the same as in Example 1.

[0139] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 74.02 N, and the peel surface rating was B; in the same control example 1 (solid content 3.50%), the peel force was 69.35 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 58.38 N, and the peel surface rating was B; in the same control example 1, the peel force was 55.38 N, and the peel surface rating was B.

[0140] Example 21 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S7 as described above. Everything else is the same as in Example 1.

[0141] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 76.98 N, and the peel surface rating was B; in the same control example 1 (solid content 3.50%), the peel force was 75.68 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 71.68 N, and the peel surface rating was B; in the same control example 1, the peel force was 69.32 N, and the peel surface rating was C.

[0142] Example 22 The difference between this embodiment and Embodiment 1 is that: A first bath impregnation solution for a two-bath impregnation method for fiber skeleton materials, wherein the active sulfur-containing compound is S8 as described above. Everything else is the same as in Example 1.

[0143] The results of the 20-minute CRA vulcanization test are as follows: In this example, the peel force was 77.84 N, and the peel surface rating was B; in the same group, the peel force of control example 1 (solid content 3.50%) was 77.38 N, and the peel surface rating was B. The results of the 60-minute CRA over-vulcanization test are as follows: In this example, the peel force was 72.14 N, and the peel surface rating was B; in the same group, the peel force of control example 1 was 69.65 N, and the peel surface rating was C.

[0144] Cords were prepared according to the methods described in Examples 1, 16-22, and Comparative Example 1, and vulcanization tests were performed on them respectively. The test methods were the same as those described above and will not be repeated here. The composition of the first bath impregnation solution with different types of functional groups of active sulfur-containing compounds is shown in Table 3 below.

[0145] Table 3: .

[0146] Analysis of the peel force data corresponding to the formulations in Table 3 shows that: Examples 1 and 16-19 demonstrate that the adhesive performance of the cords tested at 20 or 60 min CRA was significantly improved compared to Comparative Example 1 after the addition of the active sulfur-containing compound. Different second functional groups resulted in varying effects on the improvement of peel force at 20 min and 60 min. A comparison of Examples 17 and 20 shows that, with the same second functional group (triethoxysilyl), tetrasulfide S6 performed worse than disulfide S3. A comparison of Examples 19, 21, and 22 shows that mixing two functional groups or increasing the number of the same functional group in the structure of the active sulfur-containing compound did not significantly improve the adhesive performance.

[0147] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials, characterized in that, The first impregnation bath uses water as a solvent and includes epoxy compounds, blocked isocyanate compounds, and active sulfur-containing compounds; the solid content of the first impregnation bath is 1.00~5.00%; the weight of the active sulfur-containing compounds is 0.50~5.00% of the dry weight of the first impregnation bath; wherein, by weight, the dry weight of the first impregnation bath includes: 55-80 parts of blocked isocyanate compounds, 15-40 parts of epoxy compounds, and 0.05-10 parts of active sulfur-containing compounds; The structural formula of the active sulfur-containing compound is shown in general formula I: ； General Formula I; Where a is an integer from 1 to 3; p and q are each an integer from 0 to 3, and p and q are not both 0 at the same time; K1 and K2 are each independently unsubstituted or branched C1~C1. 10 Alkyl chain, C1~C 10 Heterochain, C3~C 10 cycloalkyl chain, C2~C 10 Any one or more combinations of cyclic heterochains; The heterochain is a carbon chain containing any one or more combinations of oxygen, nitrogen, and sulfur atoms; The branched chain includes any one or more combinations of alkyl chains, heterochains, cycloalkyl chains, and cyclic heterochains. R1 and R2 are each independently C3~C 12 It is any one or more combinations of alkoxysilyl, carboxyl, hydroxyl, amino, or epoxy groups.

2. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, The solid content of the first bath impregnation solution is 2.30~2.80%.

3. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, The weight of the active sulfur-containing compound is 1.00~3.00% of the dry weight of the first bath impregnation solution.

4. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, When R1 or R2 is trialkoxysilyl or dialkoxymethylsilyl, the number of carbon atoms in K1 or K2 does not exceed 4; When R1 or R2 is an epoxy group, the total number of carbon atoms in K1 or K2 does not exceed 3; When R1 or R2 is a carboxyl group, the total number of carbon atoms in K1 or K2 is no more than 6 times the number of carbon atoms in the carboxyl group; When R1 or R2 is an amino group, the total number of carbon atoms in K1 or K2 is no more than 4 times the number of amino groups; When R1 or R2 is a hydroxyl group, the total number of carbon atoms in K1 or K2 is no more than 4 times the number of oxygen atoms.

5. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, In general formula I, a=1, p=1 or 2, q=1 or 2, and K1 or K2 are each independently a C1~C3 alkylene group.

6. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, The active sulfur-containing compound is any one or a combination of cystamine dihydrochloride, 3,3-dithiodipropionic acid, bis[3-(triethoxysilyl)propyl]-disulfide, bis(2-epoxypropyl)disulfide, bis(3-hydroxypropyl)disulfide, bis[3-(triethoxysilyl)propyl]-tetrasulfide, cystine, and bis(2,3-dihydroxypropyl)disulfide.

7. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, The epoxy compound includes at least one epoxy monomer, the epoxy monomer contains at least one epoxy group, and the epoxy monomer is a water-soluble or water-dispersible compound.

8. The first bath impregnation solution for a two-bath impregnation method of fiber skeleton materials according to claim 1, characterized in that, The blocked isocyanate compound is an isocyanate protected by a blocking agent; The blocking agents include: alcohols, phenols, β-dicarbonyl compounds, oxime compounds and / or amide compounds; The isocyanate is any one or a combination of diphenylmethane-4,4'-diisocyanate, toluene diisocyanate, polymethylene polyphenyl polyisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, and terephthalic diisocyanate.

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