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Your location: Home > Related Articles > Methods for improving the stiffness of textile fibers

Methods for improving the stiffness of textile fibers

Author:QINSUN Released in:2023-10 Click:54

Battery separators are thin porous fabrics impregnated with latex adhesive, then dried in an oven to remove water. In a battery, closely spaced metal electrode plates are connected in series and immersed in a strong acidic electrolyte solution. The battery separator is placed between the metal electrode plates. On the one hand, this prevents the metal electrode plates from coming into contact with each other; on the other hand, it prevents the formation of metallic salts. class or other conductive substance to form a bridge between the metal electrode plates. Both of these issues will eventually short out the battery. The battery separator must retain enough holes to allow the electrolyte solution to flow freely between the metal electrode plates for efficient ion exchange.

When the battery separator is inserted between metal electrode plates rapproached, the flexibility of the separator material will cause certain problems, that is, the separator cannot be inserted smoothly between the metal electrode plates, which leads to difficulties in assembly operations . This problem is exacerbated by high temperatures and relative humidity.

In industry, battery separators are made of various fibers (such as cellulose, glass, polyolefin, polyester, etc.) and fillers (such as diatomaceous earth, various clays, silica, quartz, hydrocarbon polymer powder, etc.) are bonded together with an organic binder, supplied as a latex or aqueous dispersion. Battery separators made with conventional latex adhesives have some rigidity, but this decreases as temperature and relative humidity increase. Reduced rigidity can cause problems when assembling the batterie.

Many involve the need for improved battery separators. For example, US Patent No. 4,529,677 describes a new type of improved battery separator material, particularly suitable for maintenance-free batteries. This battery separator contains diatomaceous earth fillers, an acrylate copolymer binder that contains a silane coupling agent attached to the polymer backbone, and a variety of fibrous materials including polyolefins, polyesters, and fiberglass). . The acrylate copolymer adhesives used contain about 80% by weight of C1-C8 alkyl acrylate monomers, and less preferably about 80% by weight to about 30% by weight. The glass transition temperature of this copolymer is approximately 30°C to approximately 60°C. In addition, US Document No. 4,363,856 discloses organic adhesives for battery separators. The adhesive is a polymer generally available in the ccommercial, capable of forming a film, and its constituent monomers are for example methacrylic acid, acrylic acid, ethyl acrylate, methyl acrylate, etc. These monomers create flexible, hydrophilic adhesives.

One approach to achieving stiffer battery separators is to design single-phase, monomer-based latex adhesives that create stiffer, more hydrophobic polymers. To realize this idea, if a common use of latexd as a battery separator adhesive is added to replace the latex with a monomer such as styrene, alkyl-substituted styrene or isobornyl methacrylate. methyl methacrylate; The complex factors controlling the setting temperature of latex adhesives formulated on non-woven substrates are disrupted and setting cannot occur at the required temperature (which should be around 30℃ to around 60℃, which is the temperature of solidification which can be adopted(the preferred range is about 40°C to about 45°C).

When adjusting a latex adhesive composition to obtain a stiffer battery separator, there is a risk that the new composition will not solidify within the desired temperature range. Battery separators are made from a non-woven substrate of fibers and fillers, which is then impregnated with a latex adhesive. The entire mass is then dried at high temperature to cross-link the latex binder and evaporate the water contained in the latex binder to form the battery separator. During the drying operation, the latex adhesive will migrate to the surface of the battery separator as the water evaporates, which will cause the latex adhesive to be distributed unevenly. So, to avoid this problem, the latex adhesive is carefully formulated so that it remains stable when impregnated on the non-woven substrate et before large amounts of water evaporate when dried in an oven over a lower, narrower temperature range. It solidifies evenly across the entire nonwoven substrate. For latex adhesives currently used industrially in battery separators, formulations have been developed that allow the adhesive to solidify at a temperature of about 30°C to about 60°C, preferably about 40°C C at 45°C.

Heterophasic polymers have also been used in textiles to improve low temperature properties such as softness. For example, US 4,107,120 reports latex compositions in core/shell form and their use in textile materials to improve the low temperature properties of the materials. United States No. US Patent 4,277,384 further improves the above invention. The composition of latex in core/shell form and its use in dTextile materials not only improve the low temperature properties, but also improve the softness and tear resistance of the seams of textile materials. fission. US Patent Nos. 4,181,769 and 4,351,875 respectively describe finished products of the above core/shell compositions. However, none of these methods relate to the use of multi-phase latex binder compositions in which one phase improves the stiffness of the textile fibers and another phase controls the setting temperature of the latex binder. The invention not only meets the stiffness requirements of textile materials at high temperatures and high relative humidity (especially in acidic environments), but also meets the controllable coagulation temperature requirements of latex adhesives.

It is therefore an objective of the present invention to provide improved textile fibers containing an acid-resistant curable agent.bindermulti-phase latex.

Another objective of the present invention is to propose a method making it possible to improve the rigidity of textile materials.

Other objects and advantages of the present invention will become clear from the following description and claims.

The present invention relates to improved fibrous materials comprising a curable, acid-resistant, multi-phase latex binder deposited on textile fibers. This multi-phase, curable, acid-resistant latex adhesive contains a first phase copolymer which improves the stiffness of textile fibers and at least one additional copolymer which controls the setting temperature of the latex adhesive. This latex adhesive is particularly suitable for battery separators.

As used herein, the term \"textile\" refers to materials composed of natural or synthetic fibers, which may be woven or non-woven, and are characterized by their flexibilityility, their fineness and their high length/thickness ratio. . The term \"latex\", as used herein, refers to a water-insoluble polymer prepared by conventional polymerization methods (e.g., emulsion polymerization). \"Glass transition temperature\" or \"Tg\", as used herein, refers to the glass transition temperature of the polymer calculated using the Fox method (see Bulletin of the American Physical Society 1, 3, page 123 (1956) ): 1Tg=W1Tg(1)+W2Tg (2)]]> For copolymers, W1 and W2 refer to the weight fractions of the two comonomers, and Tg(1) and Tg(2) refer to the glass transition temperatures of the two corresponding homopolymers.

The latex adhesive composition of the present invention is a heterogeneous latex particle composed of at least two mutually incompatible copolymers. These mutually incompatible copolymers can exist in the following configurations, e.g.example of core/shell particles, core/shell particles whose shell layer does not surround the core, multi-core core/shell particles, interpenetrating gate particles, etc. case, the main part of the particle surface hasThe surface consists of at least one occupied external phase, while the interior of the particle is occupied by at least one internal phase.

Incompatibility Mutuality of two polymer compositions can be determined by various methods known in the art. . For example, scanning electron microscopy analysis using staining to highlight differences in appearance between phases or levels is one such method.

Multiphase latex adhesive compositions of the present invention should be expressed as containing \"*phase\" and \"Second phase\". The term \"second phase\" as used herein is not intended to exclude the possibility that one or more polymers may bere interposed between them or may precede the second phase copolymer, in which one or more polymers are formed on the copolymer phase. The present invention requires that the first phase copolymer contributes to the stiffness properties and that the other copolymer (called here \"second phase\") controls the setting of the latex binder. .

The \"* phase\" of the latex binder consists of a copolymer which is hydrophobic, stable in acidic environments and has a glass transition temperature above approximately 80°C in the dry state. To prepare this copolymer phase, materials can use a variety of* monomers or monomer mixtures. , such as methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, phenyl methacrylate, isobornyl methacrylate, styrene, 3-methylstyrene, 4-methylstyrene, 4-tert-butylstyrene, 2-chlorostyrene, 2,4-dichlorostyrene, 2,5-dichlorostyrene, 2,6-dichlorostyreneChlorostyrene, 4-chloro-2-methylstyrene, 4-chloro-3-fluorostyrene, etc. In addition to at least one of the above monomers, the copolymer must be composed of at least one multifunctional monomer (such as (as defined below). This copolymer is generated from at least one monomer * and a multifunctional group monomer. The amount of monomer * is about 95% to about 99.9%, preferably about 97% to about 99%. About 98.5%; the amount of monomer of group is from about 0.1% to about 5%, preferably from about 1% to about 3%, and preferably from about 1.5%.

As used herein, The term \"multifunctional monomer\" refers to a monomer having at least two functional groups, at least one of which coexists with other monomers used to form one of the two-phase polymers. Polymerization, and at least one other functional group remains after polymerization to react with identical or similar functional groupsres on other monomer units to cross-link the polymer. Examples of these multifunctional monomers include: amides or N-hydroxyamides of unsaturated α,β-olefinic carboxylic acids containing 4 to 10 carbon atoms (such as acrylamide, methacrylic amine, N-methylol acrylamide, N-ethanol acrylamide, N-propanol acrylamide, N-hydroxymethylmethacrylamide, N-ethanolmethacrylamide, N-hydroxymethylmaleimide, N-hydroxymethylmaleimide, N-hydroxymethylmaleamic acid, N-hydroxymethylmaleamic acid ester), N-alkylamides of vinyl aromatic acids ( such as N-hydroxymethyl-p-vinylbenzamide, etc.). Better multifunctional N-hydroxyalkylamide monomers are the N-hydroxyalkylamides of unsaturated α,β-monoolefin monocarboxylic acids, such as N-hydroxymethylacrylamide and N-hydroxymethylmethylacrylamide. Other preferred multifunctional monomer systems are near equimolar mixtures of acrylamide and N-hydroxythylacrylamide, or nearly equimolar mixtures of methacrylamide and N-hydroxymethylmethacrylamide. Multifunctional monomers confer their self-curing properties to compositions containing them. Curing can be enhanced by reaction with active hydrogen-containing resins such as triazine carboxaldehyde and urea-formaldehyde resins added to the formulation containing the resulting two-phase monomer mixture or polymer. In both cases, the composition on the textile material treated as above hardens upon drying.

If an adhesive is applied to a textile material, the higher the Tg of the * phase, the more the stiffness of the textile material is increased. The cross-bonding properties formed by this phase lead to resistance to chemical attack and reduce resistance to high temperatures. thermoplastic when applied; and binds the fibers of textile materials together when the adhesive ist applied to textile fibers and heated.

The “second phase” of latex adhesive is a copolymer that can remain stable in an acidic environment. The chosen copolymer must be stable in the presence of emulsions. Use surfactants to counter ionic and non-ionic surfactants. Coagulation occurs when heated over a narrow temperature range in the presence of surfactants. Additionally, “* phase” copolymers may also contain multifunctional monomers. Based on the total weight of the second phase, the weight of the \"second phase\" copolymer, excluding multifunctional monomers, is about 95% to about 100%, preferably about 97% to about 99% and about 98% .5%; Based on the total weight of the second phase, the weight of the multifunctional monomer is about 0% to about 5%, preferably generally about 1% to about 3%, preferably about 1.5%.

To containat least two mutually incompatible copolymers. The weight of the * phase varies from about 1% to about 85% based on the total weight of the latex particles. Based on the total weight of the latex particles, the weight of the * phase is preferably about 70% to about 80%. The second phase may comprise from about 15% to about 99% by weight, based on the total weight of the latex particles containing at least two mutually incompatible copolymers. Preferably, the second phase represents about 20% to about 30% by weight based on the total weight of the latex particles.

Latex polymers can be prepared using conventional emulsion polymerization methods well known in the art, such as the continuous emulsion polymerization methods described in U.S. Nos. 4,325,856, 4,654,397 and 4,814,373, which are incorporated herein by reference. in the context of disclosure.

It is sometimesDesirable to have chain transfer agents, such as thiols, polythiols and halides, in the polymerization mixture of each of the two phases to moderate the molecular weight of the latex polymer. Generally, from about 0.1% to about 3% by weight of chain transfer agent, based on the weight of the total monomer mixture, may be used. *The weight average molecular weight of the phase is between about 400,000 and about 2,000,000. The weight average molecular weight of the second phase is also about 400,000 to about 2,000,000. The particle size of the Latex polymer should be relatively small, preferably from about 80 nanometers to about 225 nanometers, and preferably from about 160 nanometers to about 190 nanometers. As is well known, for the same polymer skeleton, the particle size depends mainly on the type and quantity of emulsifier used in each step of the reaction.continuous emulsion polymerization.

In emulsion polymerization, anionic or cationic surfactants are used to emulsify the reactants, and they also stabilize the emulsion during subsequent storage. This surfactant is hereinafter called “stabilizing surfactant”. agent\". To the stabilized emulsion are then added a nonionic surfactant and a counterion to the stabilizing surfactant. For anionically stabilized emulsions, multivalent metal salts (such as magnesium sulfate) can hinder the stabilizing effect of the surfactants anionic, while nonionic surfactants can continue to stabilize the emulsion. But when the mixture is heated, when the temperature exceeds the cloud point of the nonionic surfactant added later but does not exceed the Tg of the binder, the emulsion of latex becomes unstable and causes coagulation.counterion, and temperature is therefore necessary toensure that the latex adhesive cures in a controlled manner. Emulsions are best stabilized with anions.

Examples of suitable anionic stabilizing surfactants include: fatty alcohol sulfates (such as sodium lauryl sulfate, etc.); alkylarylsulfonates (such as sodium or potassium cumene sulfonate), or sodium or potassium isopropylnaphthalene sulfonate, etc. ; alkali metal salts of alkyl thiosuccinates (such as sodium octyl thiosuccinate, sodium N-methyl-N-palmitoylamidoethanesulfonate, isopropylthiosuccinate, etc.), sodium oleyl sulfur carbonate (oleyl sodium, sothionate), etc.); alkali metal salts of alkaryl polyethoxyethanol sulfuric acid or sulfonic acid (such as tert-octylphenoxy polyethylene containing 1 to 5 oxyethylene units), sodium oxyethyl sulfate, etc.). Examples of suitable cationic stabilizing surfactants include: lalkylamine salts, quaternary ammonium salts, polyoxyethylene alkylamines, etc.

Suitable post-added nonionic surfactants include alkylphenoxy polyethoxylates having an alkyl group of about 7 to about 18 carbon atoms and about 6 to about 60 oxyethylene units. Alcohols (such as heptylphenoxy polyethoxyethanol, methyloctylphenoxypolyethoxyethanol, etc.); polyethoxyethanol derivative of methylene-linked alkylphenol derivatives; sulfur-containing substances (for example, the product obtained by condensing about 6 to about 60 moles of ethylene oxide with nonyl mercaptan, dodecyl mercaptan, etc., or with an alkylthiophenol containing 6 to 16 carbon atoms in the group alkyl); long-chain ethylene oxide derivatives of carboxylic acids (such as lauric acid, myritanoic acid, palmitic acid, oleic acid, etc.); or acids such as those present in tall oil containing mixtures6 to 60 units of ethylene oxide per molecule; vinyl-type condensates of long-chain alcohols (such as octanol, decanol, lauryl alcohol or cetyl alcohol); the derivatization with ethylene oxide of etherified or esterified polyols containing substances with hydrophobic hydrocarbon chains (such as sorbitan monostearate containing 6 to 60 oxyethylene units); and an ethylene oxide segment combined with one or more hydrophobic 1,2-propylene oxide segments. Mixtures of alkylphenylsulfonates and ethoxylated alkylphenols can also be used.

Counterions of stabilizing surfactants include polyvalent metal ions (if the emulsion is anionically stable) and halogens and other anionic polymers (if the emulsion is cationically stable).

Applicable multivalent metal ions, such as calcium, magnesium, zinc, barium, strontium, etc., can be used in the process ofsolidification. Complexes of multivalent metal ions (such as zinc hexaammonium, etc.) and salts of multivalent metal ions and counterions (such as chloride, acetate, bicarbonate, etc.) can be used. Magnesium sulfate is a better all-purpose metal ion salt suitable for use in battery separator adhesives. The specific types of versatile metal ions used and their quantities depend on the specific anionic surfactant and are in practice limited to those that do not negatively affect battery performance or life.

Suitable anions can be used, such as chloride, acetate, bicarbonate, sulfate, carbonate, etc. The specific types of versatile metal ions used and the quantities depend on the specific anionic surfactant and are in practice limited to those that do not negatively affect the performance or life of the battery.terie.

The preferred heterogeneous emulsified polymer used in the present invention is a two-phase emulsified polymer stabilized by a suitable anionic surfactant (such as sodium lauryl sulfate), wherein the second phase is a 98 copolymer, 5% by weight. methyl methacrylate and 1.5% by weight of methylol acrylamide, with the addition of magnesium (II) as a versatile metal ion and branched mono(octylphenyl). In the case of ethers as nonionic surfactants, the copolymer solidifies between 40°C and 50°C.

The two-phase latex of the present invention can be coated on any textile to obtain a variety of useful products. This two-phase latex is particularly suitable as a binder in applications requiring high temperatures and higher phases. Textile fibers that are relatively stiff in acidic environments and humid conditions, such as those used in the manufacture of structural structuresatified in printed circuits and battery separators.

Latex adhesives may contain additives that can improve various properties of textile materials, such as dyes, surfactants, coalescing agents, wetting agents, drying retarders, anti-foaming agents , preservatives, heat stabilizer, UV light stabilizer, etc.

Methods for applying latex adhesives to textile materials include direct coating, transfer film coating, lamination, saturation, spraying, etc.

The following examples are intended to illustrate the present invention. They do not limit the present invention, as other applications of the present invention will be obvious to those skilled in the art with common sense.

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