Detailed explanation of the types and characteristics of various softeners

Source: Dyeing and Finishing Encyclopedia goddoger

Guide

In order to give fabrics a soft, smooth, or full feel, in addition to mechanical finishing, most fabrics need to be treated with softeners. This article introduces the functions, requirements, types, and respective characteristics of softeners.

1、 The function of softener

1. Supplementing natural fibers with natural oils lost during refining, bleaching, and other processes to make the hand feel more ideal.

2. Attach to natural or synthetic fibers to improve smoothness and strength, and enhance hand feel.

3. By utilizing certain characteristics of softeners, the wearability of fabrics can be improved.

In order to achieve the above effects, softeners are generally substances with the smoothness and tactile sensation of oils and fats, which can adhere to the surface of fibers to reduce the frictional resistance between fibers and provide lubrication and softness to the fibers. Some softeners can also crosslink with reactive groups on fibers to achieve washing resistance.

2、 Requirements for softener

1. Under various soft processing conditions, the working fluid should be very stable.

2. Not reducing the whiteness and color fastness of fibers or fabrics.

3. Softened fibers or fabrics are not easily discolored by heat and should not undergo changes in color, feel, or odor during storage.

4. If the softener is lotion, its lotion stability is good.

5. According to different processing requirements, it should have appropriate properties such as water absorption, water repellent, anti-static, etc. (the selection should be based on the different requirements of the fabric). Has resistance to washing or dry cleaning.

6. There are no adverse effects after contact with human skin.

Due to the wide variety of textiles, the use of different fibers, and the varying fabric specifications and purposes, as well as different finishing requirements, the selection of softeners cannot be generalized. Therefore, it is necessary to choose softeners that meet the requirements based on the softening mechanism and function of each type of softener. In addition, the performance of each softener is always limited. To achieve good results in multiple properties, two or more softeners can be used in combination (or combined into a new softener product). The composite application of organic silicon softener and long-chain aliphatic softener can achieve good results of soft, plump, and smooth hand feel. It can also combine the application of softener with mechanical softening finishing, often achieving good results.

3、 Types of softeners

Softener is the most diverse and widely used type of dyeing and finishing auxiliaries. According to reports, among the 920 domestic and foreign auxiliary agent samples collected by the Shanghai Institute of Printing and Dyeing Technology from 1990 to 1999, 350 were softeners, accounting for 38%. There are so many varieties of softeners, based on their chemical structures, which are basically divided into two categories: long-chain fatty acids or high molecular weight polymers. The carbon hydrogen long chains in the molecular structure of long-chain fatty softeners can be arranged in an irregular curled state, forming the flexibility of the molecules. The flexible molecules adsorb onto the fiber surface to provide lubrication and reduce the dynamic and static friction coefficients between fibers.

Therefore, long-chain fat family structures generally have good softening effects, and there are not only many varieties but also large amounts of softeners. These types of softeners can be classified into anionic, cationic, nonionic, and amphoteric types based on their ionicity. In addition, for natural oils and paraffin based softeners, as they are both natural lubricating substances, they can also be classified as separate categories, but they are also classified into different ionic categories based on the different ionic properties of the emulsifiers used. Polymer softeners are mainly divided into two categories: polyethylene and organosilicon. The variety of polyethylene softeners is relatively single, and the dosage is also relatively small. The most commonly used type is still organic silicon softener. Due to the flexible helical straight chain structure of the main chain of polysiloxane, it can rotate freely 360 degrees with almost zero energy required for rotation. Therefore, the molecular structure of polysiloxane monomers conforms to the softening mechanism of textiles, which not only reduces the static and dynamic friction coefficients between fibers, but also has very small intermolecular forces and reduces the surface tension of fibers, making it an ideal material for textile softening finishing agents. Organic silicone softener is the fastest developing type of softener in recent years.

4、 The style characteristics of the sample submitted for review

Anionic softeners, in addition to soap, sulfonated oil, etc., are mainly composed of cationic compounds with long-chain alkanes such as sodium succinate octadecyl ester sulfonate and octadecyl ester sulfate, as well as anionic and nonionic compounds. Generally, it has good wettability and thermal stability, can be used in the same bath with fluorescent whitening agents, and can be used as a softener for special white fabrics. It is also suitable for cellulose fibers, which can give fabrics good water absorption, but its adsorption on fibers is similar to direct dyes, which is relatively weak, resulting in poor softness and easy washing away. In addition, due to its softening effect in the bath, it can be used for silk refining to prevent abrasion (gray damage).

5、 Non-ionic softener

Non ionic softeners are generally polyoxyethylene esters (or ethers) of decanoic acid (or alcohol), fatty esters of pentaerythritol or sorbitol. Due to the poorer adsorption of non-ionic softeners on fibers compared to ionic softeners, they can only provide a smoothing effect. But it can be used in combination with ionic softeners, has good compatibility with other materials, has good electrolyte stability, and does not have the disadvantage of yellowing fabrics. It can be used as a non durable soft finishing agent and an important component of synthetic fiber spinning oil. Some of its products can be used as silk like finishing agents for the "silk sound" of fabrics.

6、 Cationic softener

There are many varieties of this type of softener, and it is currently the most commonly used softener.

Mainly due to the negative charge of most fibers in water, cationic softeners are easily adsorbed on the surface of fibers, with strong binding ability, high temperature resistance, and washing resistance. After finishing, the fabric is full and smooth, which can improve the wear resistance and tear strength of the fabric. It also has a certain anti-static effect on synthetic fibers. Therefore, it is widely used in fabrics such as cotton, nylon, and acrylic, and there are also varieties suitable for silk. But some cationic softeners are prone to yellowing at high temperatures, accompanied by a decrease in light fastness. Cationic softeners are generally derivatives of octadecylamine or dimethyl octadecylamine, or condensates of stearic acid and polyethylene polyamine. According to their structure, they can be divided into tertiary amine softeners, quaternary ammonium salt softeners, imidazoline quaternary ammonium salt softeners, and dialkyldimethyl quaternary ammonium salt softeners.

7、 Amphoteric softener

Amphoteric softeners are a type of softener developed to improve cationic softeners. It has a strong affinity for synthetic fibers and does not suffer from yellowing or discoloration of dyes. It can also be used in the silk retraining process to make the silk feel better. Bipolar softeners can also be used together with cationic softeners to achieve synergistic effects. This type of softener generally has an alkyl amine lactone structure.

8、 Organic silicon softener

This kind of softener is the lotion or micro lotion of polysiloxane and its derivatives, which can make the fabric soft and smooth. The products include lotion polymerization, high molecular silicone oil emulsification, modification and compounding, which have basically formed a system, and there are many varieties and brands available. However, there are still significant differences in application effectiveness and performance.

1. Dimethyl silicone lotion:

This is the earliest product used in silicone softeners, and the relative molecular weight of silicone oil used as a softener is generally 60000-70000. After finishing, it can give the fabric a smooth, stiff, and refreshing feel, reduce the friction coefficient of the fabric, and improve the wear resistance and seamability of the fabric. However, due to the lack of reactive groups on its molecular chain, it cannot react with fibers or crosslink on its own, but only relies on molecular attraction and attachment to the fiber surface, resulting in poor washing resistance and limited improvement in elasticity.

2. Organic silicone hydroxy emulsion (hydroxy silicone oil lotion):

This is the most widely used silicone softener in China in the 1980s. Its relative molecular weight is generally between 60000 and 80000, and the larger the relative molecular weight, the better the softness and smoothness. Due to the end of its molecular chain and the end capping of its hydroxyl group, it can crosslink with the reactive groups of fibers or itself under the action of crosslinking agents and catalysts, forming a polymer film with certain elasticity. Therefore, it has washing resistance and can improve the elasticity of fabrics. Organic silicone emulsion is divided into cationic organic silicone emulsion and anionic organic silicone emulsion based on the different ionic properties of the emulsifier used. Although there are hydroxyl groups at the end of the molecular chain of the silicone hydroxy emulsion, which is helpful to improve its hydrophilicity and stability of the lotion, it is difficult to control the small and uniform particles of the silicone hydroxy emulsion lotion, so it is difficult to master the stability of the lotion, and it is easy to appear oil bleaching phenomenon in application, making the fabric appear defects such as oil stains that are difficult to remove. Therefore, the stability of lotion of silicone hydroxy emulsion softener is also an important index to evaluate its quality.

3. Hydrophilic soluble organosilicon (polyether hydrophilic organosilicon):

This type of silicone softener is usually a polyether and epoxy modified polysiloxane, which appears as a colorless and transparent thick liquid and can endow fabrics with good moisture absorption, breathability, and anti-static properties. Due to its non-ionic nature, it can be mixed with various additives for application. When used together with resin, it can reduce the resin's chlorine absorption and formaldehyde release; In addition to being used for resin finishing and soft finishing, it is also widely used in coating dyeing processes. It can not only improve the hand feel of fabrics affected by adhesives, but also address the drawbacks of adhesive rollers.

4. Amino modified organosilicon:

Introducing amino groups into the macromolecular chains of polydimethylsiloxane can greatly improve its properties. The introduction of amino groups can not only form a strong orientation and adsorption with fibers, reducing the friction coefficient between fibers, but also undergo chemical reactions with epoxy groups, carboxyl groups, and hydroxyl groups. Therefore, it can be applied to various fibers and their blended fabrics such as cotton, wool, silk, viscose fibers, polyester, nylon, acrylic fibers, etc. After finishing, fabrics can achieve excellent softness and resilience, with a soft and full feel, smooth and delicate texture. Generally speaking, the higher the amino content, the better the softness. But a higher amino content also means greater yellowing.

This is mainly due to the fact that the - (CH2) NH (CH2) 2NH2 on its side chain has two amino groups (primary and secondary) and a total of three active hydrogen atoms, which are easily oxidized to form chromophores. This dual amine structure has a synergistic effect on accelerating oxidation. Therefore, there must be an optimal balance between amino content and yellowing. Micro lotion made of amino modified silicone has developed rapidly in the past decade. Due to the introduction of amino groups into siloxane molecules, its hydrophilicity is improved. Therefore, the appropriate emulsifier and preparation process can make it a microemulsion with a particle size below 0.15 μ m. Because its particle size is smaller than the wavelength of visible light, it has no resistance to visible light, so it can make lotion transparent. It is precisely because its particle size is only 1/10 of the particle size in the ordinary lotion, which increases the effective particle number in the micro lotion by 103 times (if the concentration is the same). The contact opportunity between the micro lotion and the fabric is greatly increased, and the spread on the surface of the fabric is good, easy to penetrate into the fiber interior. Therefore, this product can endow the fabric with good internal softness, which is also more durable. The water solubility, storage stability, heat stability and shear stability of microemulsion products are generally better. Although commonly used diamino organosilicon softeners have good softening effects, their whiteness, water absorption, and ease of cleaning are poor, and they become more severe with the increase of amino functional groups in the polymer. To improve these drawbacks, changes in the type and quantity of amino functional groups can be achieved. The main way to change the type of amino functional group is to transform the primary amine group into a secondary or tertiary amine group. Organic silicon softeners modified with N-propylcyclohexylamine (secondary amine) and N-propylpiperazine (tertiary amine) have been developed and applied in fabric finishing. This type of softener can reduce yellowing during baking, and the organic silicon softener with Biberamine functional group has less hydrophobicity, but it makes the woven feel a bit dry. Mainly used for bleaching and soft finishing of light colored fabrics. In addition, in order to achieve a super smooth hand feel, the two ends of the dimethyl siloxane macromolecule are modified with amino groups for sealing, which can form a very neat directional arrangement on the fabric, thus obtaining excellent smooth hand feel; If some side chain groups and both end groups of polysiloxane are modified with amino groups and used as fabric finishing agents, it can improve the softness of the fabric. Nowadays, the development of organic silicon softeners is rapid, with an increasing variety and a decrease in prices. The number of applications using organic silicon softeners has increased significantly. In addition to the various types of organic silicon softeners mentioned above, there are also organic silicon softeners such as epoxy modified, amide modified, carboxyl modified, etc. Due to the current scarcity, we will not introduce them one by one here.

9、 Low molecular polyethylene lotion

This type of softener is a product of low molecular weight polyethylene that is oxidized and then emulsified. It has a certain affinity for fibers, giving fabrics a smooth hand feel, can be used in the same bath with resins, and can improve the tear strength and wear resistance reduced by resin finishing. It is an inexpensive fabric softening and smoothing agent before the promotion and application of organic silicon softeners. At present, this kind of softener is not used alone, but can be used as a composite component of various softeners, and also as a stabilizer in the hydroxyl silicone lotion.