Hot melt pressure-sensitive adhesive is a kind of pressure-sensitive adhesive, mainly by synthetic rubber, resin and rubber oil, etc. Mixed and heated into a molten state and then coated on cotton paper, non-woven fabrics or plastic film and other substrates made of a new type of adhesive tape. Mainly used for all kinds of sealing, sealing boxes, paper packaging, beverage bottle labels, sealing aluminium foil, flexible packaging and other packaging and environmental protection paper stack board, etc., to adapt to all kinds of materials.

Medical hot melt pressure sensitive adhesive is a classification of medical Hot Melt Adhesive, which is widely used in the processing and production of medical adhesive tape, infusion patch, band-aid and other medical hygiene products. Medical hot melt pressure-sensitive adhesive has both hot melt and pressure-sensitive, in the process of making adhesive products, through the special equipment to heat and melt, reflecting the hot melt, and its adhesive products such as medical adhesive tapes, bandages, etc. when used after tearing the finger pressure can be realised to achieve bonding, reflecting the pressure-sensitive.

Medical hot melt pressure sensitive adhesive requirements and standards

Medical hot melt pressure sensitive adhesive used in medical tape, elastic bandage, wound stickers, surgical incision film and other medical products, must be considered in contact with the skin and a variety of problems, briefly described below:

First, hypoallergenic

The use of medical hot melt pressure-sensitive adhesive products, the requirements will not produce skin irritation, such as redness, itching, small pimples and other allergic reactions.

Second, breathability

Hot melt pressure-sensitive adhesive products have good air permeability, it is more greatly reduce the skin allergy, and make the skin is covered with adhesive products as usual breathable breathing, for the skin perspiration, to keep the wound dry, accelerate the healing of the wound has a positive effect.

Third, adhesion

Human skin has dry and oily different, there are sweat hair more dense and no sweat hair difference, as well as smooth and rough, medical hot melt pressure-sensitive adhesive products can adapt to the needs of most people's skin texture, pasted on the skin, can be in the humid or hot environment, skin sweating, body fluid secretion, still maintain a certain degree of adhesive force, does not produce warping and quickly fall off the phenomenon.

Compatibility with skin

① peeling strength should not be too large: paste the skin of the medical hot melt pressure-sensitive adhesive products peeling strength can not be too large, to maintain a certain limit, otherwise the skin will be uncomfortable with a sense of tightness, uncovered, there is a sense of pain and will be very easy to pull up the hairs, damage to the skin.

② the initial adhesion to the skin should be good: because most of the material used in the wound or around the wound, should not be squeezed with force, so the initial adhesion of the adhesive products should be good, instantly stick to the skin.

③ No residual adhesive after tearing: no residual adhesive remains after tearing from the skin, especially at the edges around the adhesive material.

V. Adaptation of disinfection treatment

Many applied to the wound adhesive stickers, wound stickers need to be disinfected, not because of disinfectants and make the adhesive products deteriorate, the current use of gamma rays and drill ray disinfection of the adhesive effect is small, while the use of hot steam disinfection may cause changes.

Sixth, must carry out medical tests

(1) Cytotoxicity test: check the possible existence of precipitated toxic substances in the adhesive. (2) Skin irritation test: used to test to check the possibility of skin irritation by precipitates in the material after adhesive application. (3) Skin sensitisation test: Repeated trial in different age groups and on different people's skin to test for skin sensitisation reactions.

Adhesive application methods

There are various ways to apply hot melt adhesive, such as scraping, spraying, roller coating, casting, etc. Regardless of which way to apply the adhesive, the hot melt adhesive must be pre-heated into a molten state in the melting tank, and then the hot melt adhesive will be sprayed or transferred directly onto the substrate or the object to be glued by the appropriate gluing equipment. Common substrates for medical tapes are non-woven fabrics, PE films and silk fabrics. There are two types of gluing equipment: rollers and moulds.

Characteristics

Hot melt pressure sensitive adhesives used in the medical adhesive tape market must not only have appropriate applicability and thermal stability, but also non-itching, adhesive and breathable properties.

Coatability

Hot melt pressure sensitive adhesives can be applied to a variety of special substrates using special dies or rollers. However, hot-melt pressure-sensitive adhesives for medical tapes are usually highly fluid and can easily penetrate into porous substrates, resulting in overspray.

In addition, many of the substrates used for medical tapes are not able to withstand high levels of heat, and can be stretched, deformed or even damaged during application. Because of these problems, hot melt pressure sensitive adhesives are often applied to high heat resistant release paper and then transferred to various substrates.

② Allergenicity

Solvent-based adhesives used in medical tapes can cause skin irritation and require the addition of zinc oxide powder to the adhesive. The function of zinc oxide powder is two-fold: one is to reduce the skin sensitivity of solvent-based adhesives; the other is to enhance the moisture-absorbent or sweat-absorbent ability of the adhesive.

③ Adhesion

Since natural tackifying resins such as rosin or esterified rosin are not suitable for medical tapes, to obtain skin adhesion, it is necessary to rely on the softness and wettability of the hot-melt pressure-sensitive adhesive itself, i.e., the so-called visco-elasticity, and the design of hot-melt pressure-sensitive adhesives for medical tapes should place special emphasis on the mobility of the tape to the human skin. The adhesive tape must have the ability to continuously wet and adhere to the skin surface after it has been applied to the skin. Ideally, the adhesive tape should not be able to buckle and fall off due to bending movements of joints.

④ Breathability

In order to prevent skin irritation, the composition of hot-melt pressure-sensitive adhesive tapes for medical tapes usually does not contain polar substances (hydrophobic polymers). This is because they are unable to absorb moisture and perspiration. To obtain proper air permeability, the adhesive tape substrate can be perforated at appropriate intervals with the adhesive after the adhesive is applied. Alternatively, special coating and processing equipment can be used to create a non-full plate with ventilation holes in the coated surface. Both of these methods can make the medical tape obtain a certain degree of air permeability.

⑤ Other Physical Properties

The adhesive object of medical tape is human skin. The surface temperature of human skin is approximately 30-35°C at any given time and space. Therefore, apart from the fact that care should be taken during storage and transport to ensure that the hot-melt pressure-sensitive adhesive does not overflow due to high fluidity, hot-melt pressure-sensitive adhesives for medical tapes do not require special attention to heat and cold resistance, unlike tapes and labels for other applications. However, the dry and oily nature of each person's skin can make the user feel different degrees of adhesion and adhesive strength.

With the advancement of technology and the drive to improve the quality of life, the medical system has been constantly improving and innovating its products in recent years. Regardless of their function, medical dressings, patches and tapes must be combined with the appropriate adhesive to secure these applications to the skin.

Most hot melt pressure sensitive adhesives must be manufactured and applied at high temperatures (170-180°C). Therefore, they are not suitable for products that require the addition of volatile low-boiling or sublimation point drugs.

Currently, solvent adhesives, water-based adhesives and hot melt adhesives coexist in medical system products, and each does have its own special features in addition to different workability. The hypoallergenic and breathable properties of hot-melt pressure-sensitive adhesives obtained after processing are incomparable to other types of adhesives, promoting the industry's transition to a green manufacturing model.