Production process of centella paper diaper capable of preventing red fart

Abstract

The invention relates to the field of hygienic products, provides a production process of a herba centellae paper diaper for preventing red fart, and solves the problems that an existing paper diaper is relatively poor in red fart prevention effect and cannot have an antibacterial effect at the same time or skin irritation and anaphylactic reaction are possibly caused by direct contact of antibacterial substances with skin. Comprising the following steps: preparing a surface layer, preparing an antibacterial layer, preparing an absorption main body, preparing a liquid-tight bottom layer, and compounding the surface layer, the antibacterial layer, the absorption main body and the liquid-tight bottom layer into a whole, the surface layer is obtained by the following steps: S1, performing opening, carding, web forming and spunlace reinforcement on regenerated cellulose fibers to obtain regenerated cellulose non-woven fabric; and S2, spraying hydrophobic modification liquid on the upper surface of the regenerated cellulose non-woven fabric, reacting at 65-70 DEG C for 10-15 minutes, and carrying out vacuum drying for 2-4 hours to obtain the surface layer.

Description

Technical Field

[0001] The present invention relates to the field of sanitary products, and in particular to a production process of Centella asiatica diapers for preventing diaper rash. Background Art

[0002] Infants and young children have delicate skin, a thin stratum corneum, and an underdeveloped skin barrier, making them less resistant to external stimuli and friction. Diapers are products that come into direct contact with the skin of infants and young children's buttocks for extended periods of time. Factors such as their material, breathability, water absorption, and surface microenvironment may affect the health of the skin on their buttocks. During the use of traditional diapers, urine and feces come into contact with the skin for extended periods of time. In addition, the high humidity and poor breathability inside the diapers can easily breed bacteria, disrupting the skin's acid-base balance and causing diaper rash. This not only causes physical discomfort to infants and young children, such as itchy and painful skin, but can also affect their mood and sleep quality, causing distress to parents.

[0003] Diapers currently exist on the market that claim to prevent diaper rash, but most suffer from limited effectiveness and limited functionality. Some products contain chemical antimicrobial agents to inhibit bacterial growth, but these chemicals can irritate delicate infant skin, causing allergies and other adverse reactions. Other products focus on improving diaper absorbency and breathability, but these improvements, while purely physical, fail to regulate the skin's microenvironment and effectively prevent diaper rash.

[0004] Chinese patent application number CN202311849338.X discloses an antibacterial agent and an antibacterial diaper and a preparation method thereof. The antibacterial agent is a CuO / Zn-MOF composite material. The Zn-MOF material has good dispersion properties and antibacterial effects. At the same time, it has a certain specific surface area to absorb urine and keep the surface of the diaper dry. The CuO loaded on the MOF surface can be more dispersed in the antibacterial layer and can be sustained to ensure long-term antibacterial. The synergistic bactericidal effect of the two can reduce bacterial growth in humid environments. The antibacterial effect is significant, further ensuring the long-term antibacterial effect of the diaper. While performing efficient and long-lasting sterilization, it achieves good breathability and ensures a good user experience. However, the diaper adds chemical antibacterial agents to inhibit bacterial growth, which may irritate the delicate skin of infants and young children.

[0005] Chinese patent application number CN202311481380.0 discloses a pull-up sanitary product containing herbal plant extracts and its preparation method. Menstrual pants or sanitary napkins are provided with an absorbent material at the absorption part. The inside and bottom of the absorbent material contain herbal plant extracts respectively. The herbal plant extracts are divided into antibacterial components and deodorizing components. The invention uses the antibacterial components of tea leaf extract, patrinia extract and holly seed extract in combination with heparin and odor-removing components of iris vine leaf extract, which have good antibacterial effects on a variety of bacteria, ensuring that bacteria will not grow after long-term use; using galangal powder, cinnamon powder and heparin to reduce or eliminate the odor of menstrual blood, using iris vine leaf extract and polyvinyl pyrrolidone coating to mask and improve the odor of the plant extract itself, ensuring a clean odor effect; and using polyvinyl pyrrolidone to maintain the homogeneity of the plant extract in the absorbent material, achieving a balanced and long-lasting deodorizing and antibacterial effect on all parts of the menstrual pants or sanitary napkin absorbent material. However, the surface layer of the sanitary product does not have a one-way moisture conduction function. When the amount of urine is large, it cannot be quickly transferred from the surface layer to the absorbent core, which can easily cause diaper rash.

[0006] Chinese patent application number CN202110817966.4 discloses an anti-diaper and its production process, comprising a diaper body, which comprises a surface layer, a guide layer, an absorbent core and a waterproof bottom layer from the inside out. The upper surface of the surface layer is provided with an antibacterial anti-diaper layer near the baby's buttocks. The antibacterial anti-diaper layer and the tea polyphenols in the antibacterial anti-diaper layer are water-soluble substances and weakly acidic substances, which can neutralize the corrosiveness of uric acid on the baby's delicate buttocks and balance the pH value. At the same time, tea polyphenols also have antibacterial and anti-inflammatory effects, honeysuckle clears heat and detoxifies, has antibacterial and anti-inflammatory effects, wormwood has mild cold-dispelling, dehumidifying, antipruritic and anti-inflammatory effects, and chamomile oil has antibacterial and anti-inflammatory effects, thereby effectively inhibiting the growth of bacteria, protecting the buttocks and regulating the pH value. However, the antibacterial substances in the diaper are in direct contact with the skin, which may cause skin irritation and allergic reactions. Summary of the Invention

[0007] Therefore, in response to the above problems, the present invention provides a production process for Centella asiatica diapers for preventing diaper rash, which solves the problem that existing diapers are relatively poor in preventing diaper rash, cannot have antibacterial effects, or the antibacterial substances may directly contact the skin and cause skin irritation and allergic reactions.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A production process for Centella asiatica diapers for preventing red bottoms includes preparing a surface layer, an antibacterial layer, an absorbent body, and a liquid-impermeable bottom layer, and then combining the surface layer, the antibacterial layer, the absorbent body, and the liquid-impermeable bottom layer into one. The surface layer is a single-layer structure and is obtained by the following steps:

[0010] S1, opening, carding, web-forming, and hydroentanglement of the regenerated cellulose fibers to obtain a regenerated cellulose nonwoven fabric;

[0011] S2, spraying a hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric, reacting at 65° C.-70° C. for 10 min-15 min, and vacuum drying for 2 h-4 h to obtain the surface layer;

[0012] The preparation process of the hydrophobic modified liquid is as follows: weigh 0.1-0.5 parts by weight of a modifier, add it to a solvent to dissolve it, add 0.25-0.50 parts by weight of a catalyst, mix them evenly, and obtain the hydrophobic modified liquid; the structural formula of the modifier is shown in formula (1):

[0013]

[0014] In the formula, R1 is any one of -(CH2)3-, -(CH2)4-, -(CH2)5-, and -(CH2)6-.

[0015] Among them, the specific preparation process of the regenerated cellulose non-woven fabric is: the regenerated cellulose fiber raw material is opened, fed into a cotton carding machine, further opened and combed, and then the fiber web is peeled off by a web stripping mechanism and wound onto an output roller to form a fiber web. After repeating the above operation 2-3 times, a flat and uniform fiber web is obtained, and the fiber web is subjected to a process of hydroentanglement-winding-unwinding-hydroentanglement to obtain hydroentanglement reinforcement on both sides of the fiber web to obtain the regenerated cellulose non-woven fabric, which has good air permeability.

[0016] Furthermore, the skin care antibacterial liquid is composed of the following raw materials in parts by weight: 1-4 parts of Centella asiatica extract, 10-30 parts of tetrahydropyrimidine carboxylic acid, 5-10 parts of squalane, 0.3-3 parts of xanthan gum, 1-10 parts of hyaluronic acid, 5-10 parts of glycerin, 2-10 parts of butylene glycol, and 15-30 parts of deionized water.

[0017] The extraction process of the Centella asiatica extract is as follows: the dried Centella asiatica is crushed, ground, and sieved, the active ingredients of the Centella asiatica are ultrasonically extracted for 1-2 hours using a 60%-80% ethanol solution, the supernatant is filtered, and then the Centella asiatica extract is obtained by centrifugation and concentration.

[0018] The active ingredient with the highest content in Centella asiatica extract is hydroxymadecassoside, which has anti-inflammatory, antibacterial and antioxidant functions. It is safe, soothing and non-irritating, and helps to improve skin irritation.

[0019] Ectohydropyrimidine carboxylic acid is a naturally occurring organic-compatible solute that is readily soluble in water. It can inhibit the release of inflammatory factors, alleviate allergic symptoms such as contact dermatitis and eczema, and has excellent barrier repair properties. Ectohydropyrimidine carboxylic acid acts as a stabilizer, protecting the active ingredients in Centella asiatica extract. When combined with madecassoside, ectohydropyrimidine carboxylic acid reduces bacterial surface hydrophobicity and enhances madecassoside's permeability into bacterial biofilms, resulting in a synergistic effect in antibacterial and anti-inflammatory activity. It also synergizes with moisturizing ingredients such as hyaluronic acid and glycerin to enhance moisturizing effects.

[0020] Furthermore, the antibacterial layer is prepared by dipping the non-woven fabric in a skin care antibacterial liquid, rolling it, and then drying it.

[0021] Furthermore, the weight of the regenerated cellulose nonwoven fabric is 10 g / m 2 -100g / m 2 .

[0022] Furthermore, the regenerated cellulose fiber is any one of viscose fiber, cuprammonium fiber, Lyocell fiber, and Model fiber.

[0023] Furthermore, the hydrophobic modification liquid is sprayed with an atomizing electric spray gun, and the spraying amount of the hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric is 0.2 g / m 2 -2g / m 2 .

[0024] By adopting the above technical solution, the beneficial effects of the present invention are:

[0025] 1. It uses regenerated cellulose fiber as raw material, which has the softness of cotton and the smoothness of silk, and has strong moisture absorption and good skin-friendliness. Due to its fluffy and porous structure, it has excellent air permeability. It is 100% natural material, easily biodegradable, free of toxic and harmful chemicals, and has no irritation to the skin. It is an environmentally friendly green fiber. The surface layer prepared with this raw material has excellent hydrophilicity.

[0026] 2. The upper surface of the surface layer is sprayed with a hydrophobic modification liquid to introduce hydrophobic functional groups on the upper surface of the regenerated cellulose nonwoven fabric and block the hydroxyl groups on the surface of the regenerated cellulose nonwoven fabric. The lower surface is not treated to obtain a single-layer surface layer with a hydrophobic upper surface and a hydrophilic lower surface. The side close to the skin is hydrophobic, and the other side close to the absorbent layer is hydrophilic. The hydrophobic side can quickly transfer liquid to the hydrophilic side. The hydrophilic side can also act as a guide layer. When the liquid that penetrates from the hydrophobic side does not have time to be absorbed by the absorbent layer, it can quickly diffuse horizontally on the hydrophilic side under the action of capillary force to achieve a better absorption effect. This process is irreversible, that is, a surface layer with a unidirectional moisture conduction effect is obtained to avoid urine back-seepage and cause diaper rash. At the same time, the single-layer surface layer reduces the use of adhesives required for the composite surface layer.

[0027] 3. The antibacterial ingredients in the antibacterial layer include Centella asiatica extract and ectoine. Madecassoside, the most active ingredient in Centella asiatica extract, exhibits anti-inflammatory, antibacterial, and antioxidant properties. It is safe, soothing, and non-irritating, helping to improve skin irritation. Ectoine can inhibit the release of inflammatory factors, alleviate sensitive symptoms such as contact dermatitis and eczema, and has excellent barrier repair properties. The combination of these two ingredients produces a synergistic effect in terms of antibacterial and anti-inflammatory activities.

[0028] 4. Squalane is a saturated alkane oil obtained by hydrogenating the double bonds of squalene. It has a high affinity for human skin and has moisturizing, anti-aging, and skin barrier protection benefits. Glycerin and butylene glycol are effective moisturizers and are inexpensive. Hyaluronic acid has a strong water-binding ability and plays a key role in skin hydration. The skincare antibacterial liquid composition of this technical solution is scientifically formulated and can safely and effectively inhibit bacteria. Furthermore, the antibacterial substances do not come into direct contact with the skin, further preventing users from experiencing allergies, stinging, and diaper rash. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the reaction formula for modifying the regenerated cellulose nonwoven fabric with the modifier in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] Example 1

[0031] refer to Figure 1 A production process for Centella asiatica diapers for preventing red bottoms, comprising preparing a surface layer, an antibacterial layer, an absorbent body, and a liquid-impermeable bottom layer. The surface layer is a single-layer structure and is obtained by the following steps:

[0032] (1) Select regenerated cellulose fiber raw materials

[0033] Using viscose fiber as the raw material of regenerated cellulose fiber;

[0034] (2) Preparation of regenerated cellulose nonwoven fabrics

[0035] The viscose fiber is opened and fed into a carding machine for further opening and carding. The web is then peeled off by a web stripping mechanism and wound onto an output roller to form a web. The above operation is repeated twice to obtain a flat and uniform web. The web is subjected to a process of hydroentanglement-winding-unwinding-hydroentanglement to obtain hydroentanglement reinforcement on both sides of the web to obtain the regenerated cellulose nonwoven fabric. The regenerated cellulose nonwoven fabric has good air permeability and a gram weight of 10 g / m 2 -100g / m 2 ;

[0036] (3) Preparation of hydrophobic modified liquid

[0037] Weigh 0.1-0.5 parts by weight of the modifier, add it to a solvent to dissolve it, add 0.25-0.50 parts by weight of the catalyst, mix them evenly, and obtain the hydrophobic modified liquid; the structural formula of the modifier is shown in formula (2):

[0038]

[0039] (4) Preparation of surface layer

[0040] The hydrophobic modification liquid is sprayed on the upper surface of the regenerated cellulose nonwoven fabric. The hydrophobic modification liquid is sprayed with an atomizing electric spray gun. The spraying amount of the hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric is 0.2 g / m 2 -2g / m 2 , reacting at 65° C.-70° C. for 10 min-15 min, and vacuum drying for 2 h-4 h to obtain the surface layer;

[0041] refer to Figure 1 The isocyanate group (-NCO) in the modifier reacts with the hydroxyl group (-OH) in the regenerated cellulose nonwoven fabric to form a stable urethane group. At the same time, the highly hydrophobic group (alkyl, siloxane) at the other end of the modifier is also grafted onto the regenerated cellulose nonwoven fabric. This reaction does not generate any by-products, thus preventing contamination of the facing layer.

[0042] (5) Preparation of skin care antibacterial solution

[0043] The skin care antibacterial liquid is composed of the following raw materials in parts by weight: 1-4 parts of Centella asiatica extract, 10-30 parts of tetrahydropyrimidine carboxylic acid, 5-10 parts of squalane, 0.3-3 parts of xanthan gum, 1-10 parts of hyaluronic acid, 5-10 parts of glycerin, 2-10 parts of butylene glycol, and 15-30 parts of deionized water;

[0044] The extraction process of the Centella asiatica extract is as follows: crushing, grinding and sieving the dried Centella asiatica, ultrasonically extracting the active ingredients of the Centella asiatica with a 60%-80% ethanol solution for 1-2 hours, filtering the supernatant, and then centrifuging and concentrating to obtain the Centella asiatica extract;

[0045] (6) Preparation of antibacterial layer

[0046] The non-woven fabric is immersed in a skin care antibacterial liquid, rolled and then dried to obtain an antibacterial layer;

[0047] (7) The surface layer, the antibacterial layer, the absorbent body and the liquid-impermeable bottom layer are combined into one body to obtain the Centella asiatica diaper for preventing red bottom.

[0048] Furthermore, the regenerated cellulose fiber is any one of viscose fiber, cuprammonium fiber, Lyocell fiber, and Model fiber.

[0049] Example 2

[0050] A production process for Centella asiatica diapers for preventing red bottom, comprising preparing a surface layer, an antibacterial layer, an absorbent body, and a liquid-impermeable bottom layer. The surface layer is a single-layer structure and is obtained by the following steps:

[0051] (1) Select regenerated cellulose fiber raw materials

[0052] Using cuprammonium fiber as the raw material of regenerated cellulose fiber;

[0053] (2) Preparation of regenerated cellulose nonwoven fabrics

[0054] The cuprammonium fiber is opened and fed into a carding machine for further opening and carding. The web is then peeled off by a web stripping mechanism and wound onto an output roller to form a web. The above operation is repeated twice to obtain a flat and uniform web. The web is subjected to a process of hydroentanglement-winding-unwinding-hydroentanglement to obtain hydroentanglement reinforcement on both sides of the web to obtain the regenerated cellulose nonwoven fabric. The regenerated cellulose nonwoven fabric has good air permeability and a gram weight of 10 g / m 2 -100g / m 2 ;

[0055] (3) Preparation of hydrophobic modified liquid

[0056] Weigh 0.1-0.5 parts by weight of the modifier, add it to a solvent to dissolve it, add 0.25-0.50 parts by weight of the catalyst, mix them evenly, and obtain the hydrophobic modified liquid; the structural formula of the modifier is shown in formula (2):

[0057]

[0058] (4) Preparation of surface layer

[0059] The hydrophobic modification liquid is sprayed on the upper surface of the regenerated cellulose nonwoven fabric. The hydrophobic modification liquid is sprayed with an atomizing electric spray gun. The spraying amount of the hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric is 0.2 g / m 2 -2g / m 2 , reacting at 65° C.-70° C. for 10 min-15 min, and vacuum drying for 2 h-4 h to obtain the surface layer;

[0060] (5) Preparation of skin care antibacterial solution

[0061] The skin care antibacterial liquid is composed of the following raw materials in parts by weight: 1-4 parts of Centella asiatica extract, 10-30 parts of tetrahydropyrimidine carboxylic acid, 5-10 parts of squalane, 0.3-3 parts of xanthan gum, 1-10 parts of hyaluronic acid, 5-10 parts of glycerin, 2-10 parts of butylene glycol, and 15-30 parts of deionized water;

[0062] The extraction process of the Centella asiatica extract is as follows: crushing, grinding and sieving the dried Centella asiatica, ultrasonically extracting the active ingredients of the Centella asiatica with a 60%-80% ethanol solution for 1-2 hours, filtering the supernatant, and then centrifuging and concentrating to obtain the Centella asiatica extract;

[0063] (6) Preparation of antibacterial layer

[0064] The non-woven fabric is immersed in a skin care antibacterial liquid, rolled and then dried to obtain an antibacterial layer;

[0065] (7) The surface layer, the antibacterial layer, the absorbent body and the liquid-impermeable bottom layer are combined into one body to obtain the Centella asiatica diaper for preventing red bottom.

[0066] Example 3

[0067] A production process for Centella asiatica diapers for preventing red bottom, comprising preparing a surface layer, an antibacterial layer, an absorbent body, and a liquid-impermeable bottom layer. The surface layer is a single-layer structure and is obtained by the following steps:

[0068] (1) Select regenerated cellulose fiber raw materials

[0069] Lyocell fiber is used as the raw material of regenerated cellulose fiber;

[0070] (2) Preparation of regenerated cellulose nonwoven fabrics

[0071] The Lyocell fiber is opened and fed into a carding machine for further opening and carding. The web is then peeled off by a web stripping mechanism and wound onto an output roller to form a web. The above operation is repeated twice to obtain a flat and uniform web. The web is subjected to a process of hydroentanglement-winding-unwinding-hydroentanglement to obtain hydroentanglement reinforcement on both sides of the web to obtain the regenerated cellulose nonwoven fabric. The regenerated cellulose nonwoven fabric has good air permeability and a gram weight of 10 g / m 2 -100g / m 2 ;

[0072] (3) Preparation of hydrophobic modified liquid

[0073] Weigh 0.1-0.5 parts by weight of the modifier, add it to a solvent to dissolve it, add 0.25-0.50 parts by weight of the catalyst, mix them evenly, and obtain the hydrophobic modified liquid; the structural formula of the modifier is shown in formula (2):

[0074]

[0075] (4) Preparation of surface layer

[0076] The hydrophobic modification liquid is sprayed on the upper surface of the regenerated cellulose nonwoven fabric. The hydrophobic modification liquid is sprayed with an atomizing electric spray gun. The spraying amount of the hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric is 0.2 g / m 2 -2g / m 2 , reacting at 65° C.-70° C. for 10 min-15 min, and vacuum drying for 2 h-4 h to obtain the surface layer;

[0077] (5) Preparation of skin care antibacterial solution

[0078] The skin care antibacterial liquid is composed of the following raw materials in parts by weight: 1-4 parts of Centella asiatica extract, 10-30 parts of tetrahydropyrimidine carboxylic acid, 5-10 parts of squalane, 0.3-3 parts of xanthan gum, 1-10 parts of hyaluronic acid, 5-10 parts of glycerin, 2-10 parts of butylene glycol, and 15-30 parts of deionized water;

[0079] The extraction process of the Centella asiatica extract is as follows: crushing, grinding and sieving the dried Centella asiatica, ultrasonically extracting the active ingredients of the Centella asiatica with a 60%-80% ethanol solution for 1-2 hours, filtering the supernatant, and then centrifuging and concentrating to obtain the Centella asiatica extract;

[0080] (6) Preparation of antibacterial layer

[0081] The non-woven fabric is immersed in a skin care antibacterial liquid, rolled and then dried to obtain an antibacterial layer;

[0082] (7) The surface layer, the antibacterial layer, the absorbent body and the liquid-impermeable bottom layer are combined into one body to obtain the Centella asiatica diaper for preventing red bottom.

[0083] Although the present invention has been particularly shown and described in conjunction with preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims, and all such changes are within the scope of protection of the present invention.

Claims

1. A production process for Centella asiatica diapers for preventing diaper rash, comprising preparing a surface layer, an antibacterial layer, an absorbent body, and a liquid-impermeable bottom layer, and combining the surface layer, the antibacterial layer, the absorbent body, and the liquid-impermeable bottom layer into one body, characterized in that: The surface layer is a single-layer structure, and is obtained by processing the following steps: S1, opening, carding, web-forming, and hydroentanglement of the regenerated cellulose fibers to obtain a regenerated cellulose nonwoven fabric; S2, spraying a hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric, reacting at 65° C.-70° C. for 10 min-15 min, and vacuum drying for 2 h-4 h to obtain the surface layer; The preparation process of the hydrophobic modified liquid is as follows: weigh 0.1-0.5 parts by weight of a modifier, add it to a solvent to dissolve it, add 0.25-0.50 parts by weight of a catalyst, mix them evenly, and obtain the hydrophobic modified liquid; the structural formula of the modifier is shown in formula (1): In the formula, R1 is any one of -(CH2)3-, -(CH2)4-, -(CH2)5-, and -(CH2)6-.

2. The production process of the Centella asiatica diaper for preventing red bottom according to claim 1, characterized in that: The skin care antibacterial liquid is composed of the following raw materials in parts by weight: 1-4 parts of Centella asiatica extract, 10-30 parts of tetrahydropyrimidine carboxylic acid, 5-10 parts of squalane, 0.3-3 parts of xanthan gum, 1-10 parts of hyaluronic acid, 5-10 parts of glycerin, and 2-10 parts of butylene glycol.

3. The production process of the Centella asiatica diaper for preventing red bottom according to claim 1, characterized in that: The preparation process of the antibacterial layer is as follows: the non-woven fabric is immersed in a skin care antibacterial liquid, and the non-woven fabric is rolled and then dried.

4. The production process of the Centella asiatica diaper for preventing diaper rash according to claim 1, characterized in that: The weight of the regenerated cellulose nonwoven fabric is 10 g / m 2 -100g / m 2 .

5. The production process of the Centella asiatica diaper for preventing diaper rash according to claim 1, characterized in that: The regenerated cellulose fiber is any one of viscose fiber, cuprammonium fiber, Lyocell fiber and Model fiber.

6. The production process of the Centella asiatica diaper for preventing diaper rash according to claim 1, characterized in that: The hydrophobic modification liquid is sprayed with an atomizing electric spray gun, and the spraying amount of the hydrophobic modification liquid on the upper surface of the regenerated cellulose nonwoven fabric is 0.2 g / m 2 -2g / m 2 .

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