Synthesis and Application of Silicones for Textile
Silicon-containing surfactants are excellent functional surfactants for textile finishing processes. It contributes to the textiles with outstanding properties as flexibility, smooth, antistatic, hydrophobicity and thermal resistance. ‘The applications and synthesis and mechanism of modified silicones applied on textiles are introduced. And the suitable silicones featuring special structures and performances for finishing different kinds of textiles are summarized.
As for silicones for textile, silicon-containing surfactants are a type of functional surfactant with excellent properties. When applied to fabric finishing, they can endow fabrics with excellent properties such as softness, smoothness, anti-static, hydrophobicity, and heat resistance. Moreover, the raw material cost is not high, non-toxic, and environmentally friendly. Therefore, this type of surfactant is an important auxiliary agent in the textile and clothing processing industry.
Currently, many people have devoted themselves to research in this area and have obtained various modified silicone oils with different functions, which have achieved good application effects in the textile and clothing industry. Further development of various modified silicone oils for fabric finishing has important value. This article reviews the synthesis of several excellent modified silicone oils and their applications in the textile industry.
1. Amino Modified Silicone Oil – silicones for textile
1.1 Application of silicones for textile
The active groups of amino modified silicone oil can form stronger bonds with natural fibers, synthetic fibers, and blended fabrics, making the fabrics smooth, breathable, full, and soft to the touch. Synthetic fibers can achieve simulation effects such as wool, silk, silk, linen, and suede. When used as a wool fabric softening finishing agent, it can obtain fluffy, soft, slippery, waxy, wrinkle resistant and other comprehensive properties Q) The anionic diamino polysiloxane micro lotion developed by Guangzhou Andi Chemical Co., Ltd. overcomes the shortcomings of cationic or non-ionic diamino micro lotion, which is not easy to be compatible with anionic surfactants and anionic fluorescent whitening agents, and can be widely used for fabric and leather softening finishing.
The fabrics and leather treated with it have a very smooth feel and suitable elasticity. The main technical index of the product is the appearance of translucent micro lotion. PH value of 7.0~9.0, mass fraction of amino polysiloxane 30% or 20%, centrifugation at 4000r/min for 30mi without oil drift or stratification.
However, amino modified silicone oil also has several problems, such as yellowing, decreased hydrophilicity of fabrics after soft finishing, uneven distribution of amino groups, etc. Chen Rongqi proposed solutions such as changing primary amino groups to secondary or tertiary amino groups, connecting polyether to amino groups, and replacing octamethylcyclotetrasiloxane (D4) with low molar mass polyhydroxysiloxane. Zhang Hongtao et al. from Hubei University synthesized amino silicone oil using D4 and beta aminoethylaminopropylmethyldimethoxysilane (KBM-602) as raw materials. By adjusting the formula, improving the polymerization process, and adding organic acid esters and sodium bisulfite composite anti yellowing agents, the yellowing of the fabric was significantly reduced without reducing flexibility or increasing costs.
Zhu Haixia also synthesized amino silicone oil using D4 as raw material and chemically modified it. She used silane coupling agents with secondary or tertiary amino groups to reduce the content of active hydrogen, and the oxidation of high position hindered secondary amino groups requires higher energy. At the same time, high position hindered amino groups also have the function of scavenging free radicals, greatly reducing their yellowing.
After testing, the product synthesized by this method not only reduces yellowing but also endows the product with good hydrophilicity. This product is an anionic lotion, which can be directly soluble in water and has good stability. It can be used in the same bath with other dyeing and finishing auxiliaries, completely solving the worries of printing and dyeing factories when using amino silicone oil.
The composition and structure of organic silicon molecular chains have a significant impact on the finishing effect of organic silicon fabric finishing agents. Nowadays, people generally use various microemulsions of modified silicone oil or other polymer lotion to improve the comprehensive properties of finished fabrics. The micro lotion compounded with epoxy silicone oil can make the fabric smooth, soft and elastic.
The crosslinking degree of silicone oil molecules also affects the finishing effect. In the process of fabric finishing, silicone oil lotion is adsorbed on the fiber surface. After drying, silicone oil with a certain degree of crosslinking can be firmly coated on the fiber surface to increase washing resistance and finishing effect. Trialkoxysilane can be added to the silicone micro lotion to make it cross-linked; However, the amount of crosslinking agent must be strictly controlled to prevent gel formation during the preparation, storage or use of micro lotion.
In addition, the mass fraction of silicone oil and the content of modified groups in the micro lotion also affect the finishing effect. Generally speaking, the higher the mole fraction of silicone oil, the better the film-forming ability on the fabric surface, and the better the hand feel and elasticity.
Li Qun synthesized amino silicone oil using bulk polymerization method and applied it to woolen fabrics. The amino silicone oil synthesized by this method is suitable for preparing the soft finishing agent LQ-88 for woolen fabrics. With the increase of the dosage of amino coupling agent, the ammonia value of amino modified silicone oil increases, and the viscosity and hand feel continue to improve.
The disadvantage is that the increase in polymerization degree and the enhancement of hydrogen bonds cause the viscosity of amino silicone oil to rapidly increase. It is possible to consider using polymerization inhibitors to control the reaction. The elastic recovery angle (warp+weft) of the spun wool fabric after LQ-88 finishing is greater than 300, with an increase of more than 12.33%; Tear strength greater than 240N, with an increase of 47.38%; The tactile sensation increased by 4, but the water absorption decreased by 29.80%.
Wei Ju studied the application of amino silicone softener on linen fabric. Due to its high content of non cellulose components, linen fabrics have a rough and hard feel and require soft finishing. Aminosilicone is a good choice. After experimental testing, the stiffness of linen fabric treated with amino silicone softener decreased to 2.62cm, a decrease of 0.59cm from the original 3.21cm; The softness is 8.7cm, an increase of 0.3cm from the previous 8.4cm, indicating a significant softening effect. And it has good washing resistance after sorting. The excellent flexibility of amino silicone is determined by its unique chemical structure, as shown in the figure below, and its mechanism of interaction with cellulose is shown in the figure below.
1.2 Synthesis of silicones for textile
The polymerization mechanism of one-step synthesis of amino modified silicone micro lotion is D4 ring opening polymerization and silane coupling agent copolymerization modification. The reaction equation is shown in the following figure.
The amount of silane coupling agent 602 added must be moderate. If the amount added is too small, the modification effect will not be achieved; Excessive amounts result in waste and increase costs. The ammonia value of the sample increases with the dosage of 602 and reaches a maximum value before remaining unchanged. The sample is used for the finishing of cotton and synthetic fibers (nylon, polyester), and after soaking, rolling, pre drying, and baking, it has excellent softening effect. The product produced by the above reaction equation has received positive feedback from users.
1.3 Characterization of Amino Silicone Oil
The molecular structure of silicone oil is usually characterized by three parameters: ammonia value, viscosity, and reactivity. Common parameters that indicate amino content include amino mass fraction, amino modification rate, and ammonia equivalent. Amino silicone oil with high viscosity has good film-forming properties on the surface of fibers, as well as good hand feel and elasticity; Amino silicone oil with reactive end groups at the molecular end exhibits self crosslinking when treating fibers. Choosing the appropriate crosslinking agent will result in a softer, smoother, and more elastic finishing effect.
2. Polyether modified silicone oil
2.1 Application
Polyether modified silicone oil can improve the hydrophilicity, anti-static and anti fouling properties of fabrics, and is easy to emulsify, not easy to float oil. Sometimes it can also be used in the same bath as dyeing in the process, making it the most commonly used type in the textile industry. Adjusting the relative molecular weight of siloxane segments in copolymers can highlight or weaken the characteristics of organosilicon, such as smoothness and flexibility.
Similarly, changing the relative molecular weight of the polyether segment can increase or decrease the proportion of organosilicon in the molecule, which can also affect the properties of the copolymer. The hydrophilic organic silicon fabric finishing agent NTF1, produced by Nantong Synthetic Materials Factory through solvent-free catalytic addition reaction, has excellent breathability, moisture absorption, and anti-static properties. It can be used in the same bath with various additives and dyes, and there is no problem of emulsion breaking and bleaching Polyether modified silicone oil also has good compatibility with other finishing agents.
2.2 Synthesis – silicones for textile
a. Direct Addition Reaction
b. Alcoholysis synthesis
Si-H bonds have properties similar to metal hydrides and can undergo addition reactions with carbon-carbon double and triple bonds. The hydrosilylation reaction of olefins can be divided into free radical type and ionic type. Free radical type hydrosilylation reaction can be carried out at 200-600 ℃ and 0.2-75MPa, and can also be completed under ultraviolet irradiation or peroxide action.
In the free radical hydrosilylation reaction, the concentration of the product is closely related to that of the reactants. When there is an excess of silicon hydrogen, addition reactions mainly occur, but if the olefin has strong self-polymerization ability, free radical polymerization reactions are difficult to avoid. During the reaction, the Si-H bond first breaks to generate silicon radicals, which then add to the carbon-carbon double bond, and finally take away the hydrogen atom to produce polyether silicones for textile oil products.
3. Epoxy Modified Silicone Oil – silicones for textile
3.1 Application
Epoxy modified water-soluble silicone oil containing both epoxy groups and polyether chains exhibits reactivity with epoxy groups, mainly manifested in the ability to form covalent bonds with functional groups such as hydroxyl, amino, or carboxyl groups in fibers, firmly bonding with fibers and improving the durability of the finishing effect; And the processed fabric does not turn yellow at high temperatures, and the fibers become loose, which is the difference from amino modified silicone oil.
At the same time, polyether segments can improve the hydrophilicity and antistatic properties of silicone oil, and their use in textile finishing has many advantages. Cheng Jianhua et al. synthesized epoxy modified silicones for textile oil and explored the influencing factors of the reaction. If used in combination with amino modified organosilicon, it can achieve a very ideal softening effect.
3.2 Synthesis
The acidity of active hydrogen in alcohol compounds is extremely weak. In the absence of a catalyst, the hydroxyl groups of alcohols generally do not react with epoxy compounds below 200 ℃. Both acid and base can be used as catalysts for this reaction.
4. Quaternized silane – silicones for textile
4.1 Application
Quaternary ammonium organosilane has antibacterial properties, can bond with fabrics through chemical bonds, has long-lasting antibacterial effects without developing drug resistance, and is considered one of the highly efficient and broad-spectrum non pharmacological antibacterial products with high safety for human body and environment.
At present, quaternized organosilane has been applied to the functional finishing of underwear and bedding. In recent years, with the prevalence of various infectious bacteria, quaternized silane and its processed antibacterial fabrics are expected to provide effective barriers for people’s physical and mental health. An Qiufeng et al. synthesized N, N-dimethylN-octadecylaminopropyltrimethoxysilane quaternary ammonium salt (BFS) and measured its antibacterial and softening effects on cotton fabrics.
After testing, it was found that using quaternized silane alone for cotton fabric finishing resulted in a larger wrinkle recovery angle and better elasticity, but poorer whiteness and less than ideal hand feel. Additionally, the tear strength and fracture strength were lower than those of blank cotton, which may be due to excessive crosslinking of tri functional silane. Adding amino silicone microemulsion softener in the same bath can effectively improve these properties.
4.2 Synthesis
This reaction requires continuous reaction for 24-36 hours, filtration to remove insoluble antioxidant residues, vacuum recovery of solvents and unreacted substances, and addition of solid acid to remove trace amounts of residual tertiary amines and decolorization to obtain light yellow transparent liquid quaternized silane BFS.
5. Piperazine based modified silicon lotion – silicones for textile
5.1 Application
Piperazinyl modified silicone lotion used as softening agent is mostly prepared by two-step method (piperazinyl modified silicone oil is synthesized through bulk polymerization, and then emulsified with appropriate emulsifier) or one-step method (pre emulsification method). To make the operation method simpler, Su Xichun uses silane coupling agent containing piperazinyl group to conduct lotion copolymerization with silicone monomer, and makes translucent piperazinyl modified silicone lotion by directly dropping monomer.
At the same time, it also adds new varieties for low yellowing amino modified silicones for textile lotion. Amino modified organosilicon lotion can be widely used for the softening and finishing of various fabrics, making cotton, linen, silk, wool, polyester, polyamide and acrylic fibers and other fabrics soft, smooth, plump feel and soft and shiny appearance.
Piperazine based modified silicon lotion can be used for fabric resin finishing, which can significantly improve the elasticity of the fabric and give the fabric a good feel. The product has excellent centrifugation, electrolyte resistance, acid and alkali resistance, hard water resistance, heat resistance, placement and dilution stability, and can be diluted with water at will, which has a good finishing effect on pure cotton fabrics.
The piperazine group in the silicon lotion can interact with the hydroxyl and carboxyl groups on the surface of the fiber to form a hydrogen bond, which makes the organic silicon and the fiber form a very strong directional adsorption, reduces the friction coefficient between the fibers, thus giving the fabric a soft and smooth feel, especially suitable for the soft finishing of light-colored fabrics.
5.2 Synthesis
The reaction equation for synthesizing piperazine modified silicon is as follows:
This polymerization reaction belongs to anionic polymerization. Firstly, the alkaline micelles undergo ion exchange with cationic emulsifiers, generating quaternary ammonium bases located on the surface of the solubilized micelles. Under the initiation of this quaternary ammonium base, D4 rings in or on the surface of the micelles form active centers; Subsequently, chain growth and condensation reactions are carried out: at the same time, silane coupling agents undergo hydrolysis and condensation reactions, accompanied by copolymerization reactions with D4 condensation products.
6. Mercaptoalkylalkoxysilane – silicones for textile
6.1 Application:
Mercaptoalkyl alkoxysilane is a kind of organosilicon compound that is widely used. Its lotion can be used for shrink proof and wrinkle proof finishing of silk fabrics. China is a big country in silk production, but the finishing technology of silk is relatively backward. Silk fabrics are prone to wrinkle after washing, and their dimensional stability is poor, affecting their beauty. Gu Wenxiu et al. synthesized mercapto based silane coupling agents using compounds such as methyldichlorosilane, methyltrichlorosilane, trichlorosilane, allyl chloride, anhydrous methanol or ethanol, thiourea, and ammonia as raw materials. Through chlorination, hydrosilylation, alcoholysis, and thiolation reactions, mercapto based silane coupling agents were used as raw materials for silk fabric finishing.
6.2 Synthesis
The equation for synthesizing thiol-based silane coupling agent is as follows:
7. Other types – silicones for textile
Other types of modification methods include alcohol modification, carboxyl modification, ester modification, etc. The comparison of the structural and performance characteristics of these types of modified silicone oils is shown in the table below.
| Modified Silicone Oil | Representative Structure | Main Features |
| Carboxyl modified silicone oil | -(CH2)nCOOH | exhibits reactivity and lubricity, but increases surface tension |
| Alcohol modified silicone oil | R-OH | improve the dyeing, heat resistance, and water resistance of fabrics |
| Ester modified silicone oil | RCOOR1 | Make the fabric soft, smooth, and elastic; Suitable for soft finishing of synthetic and cotton polyester blended fabrics |
Organic Silicones for textile is a promising additive in the textile industry, which is beneficial for improving the wearability and other properties of textiles.