Soft calendaring finishing method for high-smoothness and high-breathability paper-based facing material

Abstract

The invention relates to the field of papermaking, and particularly provides a soft calendaring finishing method of a high-smoothness and high-breathability paper-based facing material. The soft calendaring finishing method comprises the following steps: S100, coating a paper base with an inorganic filler coating liquid to obtain a paper base with a coating; and S200, carrying out pre-humidifying treatment on the paper base with the coating, and then carrying out soft calendering treatment on the paper base with the coating under the assistance of steam, so as to obtain the high-smoothness and high-breathability paper-based facing material. Wherein the steam assistance is to spray steam to the surface of the paper base with the coating. According to the soft calendaring finishing method of the high-smoothness and high-breathability paper-based facing material, the steam-assisted soft calendaring treatment step is introduced after the inorganic filler is coated, so that the surface smoothness and glossiness of the paper base are improved, and meanwhile, the microporous structure and breathability of the paper are effectively kept.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and in particular to a soft calendering finishing method for a high-smoothness and high-breathability paper-based finishing material. Background Art

[0002] High-smoothness and high-permeability paper-based finishing material is a composite material with a natural fiber paper base as the base material. The surface is specially coated and physically finished. It has a mirror gloss and delicate feel while still maintaining good air or gas exchange capabilities. Due to its high smoothness, high gloss and high permeability, it is often used in green packaging, environmentally friendly furniture, wall decoration, biodegradable decorative laminate structures and other scenarios.

[0003] High-smoothness and high-permeability paper-based finishing materials mainly achieve high smoothness, high gloss, and high permeability through calendering and finishing. However, the current calendering method usually uses a combination of steel rollers and steel rollers or iron rollers. The calendering temperature is usually greater than 120s℃, and the linear pressure is as high as 300N / mm. This will cause the pore structure of the paper to collapse, and the permeability to drop sharply, which can easily cause the paper to become brittle, warp, and even yellow. The finishing method usually improves the smoothness and mirror effect through heat setting, but this will cause the high temperature to soften the coating, resulting in the closure of micropores. In addition, this method has high heat loss and is not suitable for environmental protection requirements, making it difficult for the final paper-based finishing material to have high gloss, high smoothness, and high permeability. Therefore, there is an urgent need to provide a soft calendering finishing method for high-smoothness and high-permeability paper-based finishing materials. Summary of the Invention

[0004] The present invention aims to solve at least one of the above technical problems.

[0005] The present invention provides a soft calendering finishing method for a highly smooth and highly breathable paper-based finishing material, comprising: S100, coating a paper base with an inorganic filler coating liquid to obtain a paper base with a coating; S200, pre-humidifying the coated paper base, and then soft-calendering the coated paper base with the assistance of steam to obtain a highly smooth and highly breathable paper-based finishing material; The steam-assisted method is to spray steam onto the surface of the paper base having the coating.

[0006] In the above technical features, after the pre-humidification treatment, the moisture content of the paper base with the coating is 7-10%.

[0007] In any of the above technical features, the steam used for steam assistance includes water vapor or liquid carbon dioxide; and / or the temperature of the steam assistance is 30-50°C; and / or the roller temperature of the soft calendering treatment is 70-90°C.

[0008] In any of the above technical features, the preparation method further comprises: S300: After the soft calendering treatment, the coated paper base is subjected to a cooling and moisture removal treatment.

[0009] In any of the above technical features, the cooling and dehumidification treatment includes water-cooled roller treatment or negative pressure dehumidification treatment.

[0010] In any of the above technical features, the method for preparing the inorganic filler coating liquid comprises: S100, adding a dispersant to deionized water for a first stirring process, and adding an inorganic filler during the first stirring process to obtain an inorganic filler dispersion; S200 , performing a second stirring treatment on the inorganic filler dispersion, and sequentially adding acrylic acid-polyurethane emulsion and auxiliary agents during the second stirring treatment to obtain an inorganic filler coating liquid.

[0011] In any of the above technical features, the particle size of the inorganic filler is 1-3 μm.

[0012] In any of the above technical features, the rotation speed of the first stirring treatment is 1500-2000 rpm; and / or the time of the first stirring treatment is 20-30 min; and / or the rotation speed of the second stirring treatment is 300-600 rpm; and / or the time of the second stirring treatment is 10-20 min.

[0013] In any of the above technical features, the inorganic filler includes at least one of calcium carbonate, silicon dioxide and talc, or a combination thereof; and / or the auxiliary agent includes at least one of a defoaming agent, a preservative, a thickener and a pH regulator, or a combination thereof.

[0014] In any of the above technical features, the viscosity of the inorganic filler coating liquid is 1000-1200 mPa·s; and / or the pH of the inorganic filler coating liquid is 7-8.

[0015] After adopting the technical solution of the present invention, the technical effects that can be achieved are as follows: 1. The soft calendering finishing method for a highly smooth and breathable paper-based finishing material provided by the present invention incorporates a steam-assisted soft calendering step after the inorganic filler coating. This improves the surface smoothness and glossiness of the paper while effectively maintaining the paper's microporous structure and breathability. 2. Steam-assisted soft calendering allows trace amounts of moisture from the steam to enter the emulsion coating, softening the surface particle bonds and imparting slight fluidity. This allows the gaps between fillers to self-adjust and level during subsequent soft calendering, resulting in a more uniform surface without collapsing the inorganic filler coating. Furthermore, steam-assisted calendering can alleviate moisture gradients and stress differences between the paper base and the coating, effectively reducing issues like indentation, edge cracking, warping, or peeling. 3. Cooling and dehumidification after soft calendering helps to quickly reduce the temperature to near room temperature, prevent warping and curling, reduce residual moisture, fix the coating surface structure and gloss, avoid mirror layer adhesion caused by slow cooling, and improve paper dimensional stability and post-processing performance. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0017] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below.

[0019] In the related art, high-smoothness and high-permeability paper-based finishing materials mainly obtain properties such as high smoothness, high gloss and high permeability through calendering and finishing and shaping. The calendering is mainly carried out by steel rollers combined with steel rollers or iron rollers. The temperature is usually greater than 120s℃ and the linear pressure is as high as 300N / mm. This will cause the pore structure of the paper to collapse and the permeability to drop sharply, which can easily cause the paper to become brittle, warp, or even yellow. The finishing method usually adopts the heat setting method, but this will cause the high temperature to soften the coating, resulting in the closure of micropores. In addition, this method has large heat loss and is not suitable for environmental protection requirements, making it difficult for the final paper-based finishing material to have high gloss, high smoothness and high permeability. In view of this, the present invention provides a soft calendering finishing method for a highly smooth and breathable paper-based finishing material, which is achieved by coating an inorganic filler and performing a soft calendering treatment with the assistance of steam, so that the paper-based finishing material has high gloss, high smoothness and high permeability.

[0020] Specifically, the present invention provides a soft calendering finishing method for a highly smooth and highly breathable paper-based finishing material, comprising: S100, coating a paper base with an inorganic filler coating liquid to obtain a paper base with a coating; S200, pre-humidifying the coated paper base, and then soft-calendering the coated paper base with the assistance of steam to obtain a highly smooth and highly breathable paper base finishing material.

[0021] Preferably, the soft calendering finishing method for a highly smooth and highly breathable paper-based finishing material provided by the present invention introduces a steam-assisted soft calendering treatment step after the inorganic filler is coated, thereby improving the surface smoothness and glossiness of the paper base while effectively maintaining the microporous structure and air permeability of the paper; first, the paper base is coated with an inorganic filler coating liquid, and the inorganic filler is a non-film-forming particulate material. After coating, it will not form a dense continuous film, but will construct a highly microporous surface structure. Since the particle size and specific surface area of ​​the inorganic filler are adjustable, a large number of connecting channels and micro-gap structures are formed in the coating during the drying process, which are interconnected with the pores of the paper base itself, effectively maintaining the overall air permeability, and the inorganic filler coating helps to retain sufficient gas exchange capacity after steam-assisted calendering; the inorganic filler is preferably at least one of calcium carbonate, silicon dioxide and talc or a combination thereof, and the particle size is preferably fine particles of 1-3 μm, which can form a preliminary smooth surface frame, which is convenient for polishing in the subsequent soft calendering treatment to avoid compaction of the microporous structure.

[0022] Preferably, after the inorganic filler coating is applied, a drying treatment should be performed to form a stable coating on the surface of the paper base; then the coated paper base is placed in a constant humidity chamber at RH65-75% for pre-humidification treatment for 2-4 hours to prevent the paper base from being damaged by drying or uneven moisture absorption during hot pressing, causing cracks in the coating. After the pre-humidification treatment, the moisture content of the paper base is 7-10%; the coated paper base is then soft-calendered with the assistance of steam, that is, before the soft calendering treatment, a spray-type steam nozzle is used to evenly spray a layer of mist-like steam before the paper enters the calendering roller. The position of the steam nozzle is preferably 20-50 cm in front of the calendering roller. The trace moisture of the steam can enter the emulsion coating, softening the surface particle joints and imparting slight fluidity, so that during the subsequent soft calendering treatment, the gaps between the fillers can be self-adjusted and filled, forming a more uniform surface without collapsing the surface of the inorganic filler coating; and steam assistance can alleviate the paper The humidity gradient and stress difference between the substrate and the coating effectively reduce problems such as indentation, edge bursting, warping or peeling of the paper. The steam used for steam assistance includes water vapor or liquid carbon dioxide, with a temperature of 30-50°C. Water vapor can slightly moisten and soften the coating without high temperature, protecting the coating structure. Liquid carbon dioxide has low energy consumption, fast response, is environmentally friendly and does not introduce excess moisture. At temperatures of 30-50°C, the paper surface is slightly wetted by the condensed microdroplets of steam and carbon dioxide, increasing the moisture content of the coating surface by 1-3%. Inorganic filler coatings enter the glass transition phase in this temperature range, and the surface particles undergo local migration or deformation, giving the coating plastic flow. In the subsequent soft calendering treatment, the surface particles are rearranged, achieving micro-polishing, flattening and reconstruction between particles. In addition, the steam acts only on the coating surface within 1-3μm, preserving the pore structure of its lower part and the paper base, allowing the finishing material to achieve high gloss while still maintaining high air permeability.

[0023] Furthermore, the soft calendering treatment uses a combination of elastic rollers and constant temperature steel rollers, with flexible pressing, which can achieve stable linear pressure distribution and wider coverage of the pressure zone, avoiding obvious ripples or friction indentations on the edge of the calendered belt; the roller temperature for soft calendering treatment is 70-90°C. When calendering at this temperature, the particles on the coating surface will be slightly compressed and the edges of the micropores will be filled, but the internal skeleton structure can still remain stable.

[0024] Preferably, the preparation method further comprises: S300, after the soft calendering treatment, cooling and dehumidifying the paper base with the coating. After the soft calendering treatment, there is usually residual heat on the paper base and the coating surface, and the surface coating is in a slightly moist state where the surface coating is not completely and stably solidified. Therefore, cooling and dehumidifying helps to quickly reduce the temperature to near room temperature, prevent heat warping and curling, and can reduce residual moisture, fix the surface structure and gloss of the coating, avoid the mirror layer from sticking back due to slow cooling, and improve the dimensional stability and post-processing performance of the paper; cooling and dehumidifying Wet treatment includes water-cooled roller treatment or negative pressure dehumidification treatment. Water-cooled roller treatment can quickly take away surface heat, avoid soft reflow or thermal warping of the coating, balance the tension difference between the two sides of the paper, reduce warping and curling problems after calendering, and further improve the flatness of the paper base, thereby making the surface gloss more mirror-like and non-fogging, and enhancing the stability of the finish; negative pressure dehumidification treatment can quickly remove water vapor trapped in the inner layer of the paper or in the microporous gaps, preventing bubbling or stickiness caused by moisture, thereby helping to improve the inner layer air permeability uniformity and dimensional stability of the finishing material.

[0025] Preferably, the preparation method of the inorganic filler coating liquid comprises: S100, adding a dispersant to deionized water for a first stirring process, and adding an inorganic filler during the first stirring process to obtain an inorganic filler dispersion; S200 , performing a second stirring treatment on the inorganic filler dispersion, and sequentially adding acrylic acid-polyurethane emulsion and auxiliary agents during the second stirring treatment to obtain an inorganic filler coating liquid.

[0026] Preferably, the inorganic filler coating liquid is stirred in two stages and functional components are added step by step, which can form a stable, uniform and suitable microporous coating system; first, the dispersant is added to the deionized water for the first stirring treatment. The dispersant is added in advance to effectively control the agglomeration of the filler. After the inorganic filler is added, it can be preferentially adsorbed on the surface of the inorganic filler to form an electrostatic or spatial steric barrier; the inorganic filler is added during the first stirring treatment, and the speed of the first stirring treatment is 1500-2000rpm, and the time is 20-30min, to avoid local concentration and agglomeration caused by instantaneous accumulation of the filler, maintain the fluidity of the system, and facilitate the formation of a dispersed phase with fine particle size and uniform distribution.

[0027] Furthermore, the inorganic filler dispersion is subjected to a second stirring treatment, and acrylic-polyurethane emulsion and additives are added in sequence during the second stirring treatment. The polyurethane segment provides flexibility and adhesion, the acrylic segment imparts hardness and water resistance, and forms an organic-inorganic composite network with the inorganic filler interface, which has both microporous support and film-forming bonding functions, can avoid cracking, falling off or powdering of the coating, and is suitable for subsequent soft calendering treatment. The rotation speed of the second stirring treatment is preferably 300-600rpm, and the time is 10-20min; the additives preferably include at least one of a defoamer, a preservative, a thickener and a pH regulator, or a combination thereof. The defoamer can inhibit bubbles and increase the density of the coating. The preservative can extend the shelf life of the coating solution and ensure industrial adaptability. The thickener can adjust the rheological properties and adapt to various processes such as scraper, rod coating, and roller coating. The pH regulator can adjust the pH so that the final inorganic filler coating solution maintains a relatively stable pH.

[0028] Preferably, the viscosity of the inorganic filler coating liquid is 1000-1200 mPa·s, at which point the fluidity is moderate, and it can be spread well without splashing or sagging, and is suitable for a variety of coating equipment. The coating in this viscosity range has good leveling properties and is not prone to pinholes or bubbles, which is beneficial to improving the surface uniformity and visual gloss of the facing paper; the pH of the inorganic filler coating liquid is 7-8, which can maintain the charge shielding effect of the dispersant in the solution, and the acrylic-polyurethane emulsion is not prone to acid hydrolysis or alkaline hydrolysis reactions, which is beneficial to the physical crosslinking stability of the film-forming process and prevents the flocculation and sedimentation of the inorganic filler.

[0029] Example 1 This embodiment provides a soft calendering finishing method for a highly smooth and air-permeable paper-based finishing material, comprising: S100, coating a paper base with a calcium carbonate coating liquid having a particle size of 1 μm to obtain a paper base having a coating; S200, placing the coated paper base in a constant humidity chamber at RH 65% for pre-humidification treatment for 4 hours, and then performing soft calendering treatment on the coated paper base with the assistance of steam at a roller temperature of 70°C to obtain a highly smooth and highly breathable paper-based finishing material; Among them, steam assistance is to use a spray-type steam nozzle to evenly spray a layer of 30°C mist-like water vapor to the surface of the coated paper base before the paper enters the calendering roller. The steam nozzle is located 20 cm in front of the calendering roller.

[0030] Example 2 This embodiment provides a soft calendering finishing method for a highly smooth and air-permeable paper-based finishing material, comprising: S100, coating a paper base with a calcium carbonate and silicon dioxide coating solution having a particle size of 3 μm to obtain a paper base having a coating; S200, placing the coated paper base in a constant humidity chamber at RH 75% for pre-humidification treatment for 2 hours, and then performing soft calendering treatment on the coated paper base with the assistance of steam at a roller temperature of 90° C. to obtain a highly smooth and highly breathable paper-based finishing material; S300, after the soft calendering treatment, the coated paper base is subjected to a water-cooling roller treatment; Among them, steam assistance is to use a spray steam nozzle to evenly spray a layer of 50°C mist-like liquid carbon dioxide vapor to the surface of the coated paper base before the paper enters the calendering roller. The steam nozzle is located 50 cm in front of the calendering roller.

[0031] Example 3 This embodiment provides a soft calendering finishing method for a highly smooth and air-permeable paper-based finishing material, comprising: S100, coating a paper base with talc powder and a silica coating solution having a particle size of 2 μm to obtain a paper base having a coating; S200, placing the coated paper base in a constant humidity chamber at RH 70% for pre-humidification treatment for 3 hours, and then performing soft calendering treatment on the coated paper base with the assistance of steam at a roller temperature of 80° C. to obtain a highly smooth and highly breathable paper-based finishing material; S300, after the soft calendering treatment, the coated paper base is subjected to a water-cooling roller treatment; The steam-assisted method uses a spray-type steam nozzle to evenly spray a layer of 30°C mist-like liquid carbon dioxide vapor onto the surface of the coated paper before the paper enters the calender roller. The steam nozzle is located 45 cm in front of the calender roller. The preparation method of the inorganic filler coating liquid comprises: S100, adding a dispersant to deionized water and performing a first stirring process at a rotation speed of 1500 rpm for 30 minutes, adding talc and silicon dioxide during the first stirring process to obtain an inorganic filler dispersion; S200, performing a second stirring treatment on the inorganic filler dispersion at a rotation speed of 300 rpm for 20 minutes, and sequentially adding an acrylic acid-polyurethane emulsion and an auxiliary agent during the second stirring treatment to obtain an inorganic filler coating liquid; The auxiliary agents include a defoamer, a preservative, a thickener and a pH adjuster. The viscosity of the inorganic filler coating liquid is 1000 mPa·s and the pH is 7.

[0032] Example 4 This embodiment provides a soft calendering finishing method for a highly smooth and air-permeable paper-based finishing material, comprising: S100, coating a paper base with talc powder and a silica coating solution having a particle size of 2 μm to obtain a paper base having a coating; S200, placing the coated paper base in a constant humidity chamber at RH 70% for pre-humidification treatment for 3 hours, and then performing soft calendering treatment on the coated paper base with the assistance of steam at a roller temperature of 80° C. to obtain a highly smooth and highly breathable paper-based finishing material; S300, after the soft calendering treatment, the coated paper base is subjected to a water-cooling roller treatment; The steam-assisted method uses a spray-type steam nozzle to evenly spray a layer of 30°C mist-like liquid carbon dioxide vapor onto the surface of the coated paper before the paper enters the calender roller. The steam nozzle is located 45 cm in front of the calender roller. The preparation method of the inorganic filler coating liquid comprises: S100, adding a dispersant to deionized water and performing a first stirring process at a rotation speed of 2000 rpm for 20 minutes, adding talc and silicon dioxide during the first stirring process to obtain an inorganic filler dispersion; S200, performing a second stirring treatment on the inorganic filler dispersion at a rotation speed of 600 rpm for 10 minutes, and sequentially adding an acrylic acid-polyurethane emulsion and an auxiliary agent during the second stirring treatment to obtain an inorganic filler coating liquid; The auxiliary agents include a defoamer, a preservative, a thickener and a pH adjuster. The viscosity of the inorganic filler coating liquid is 1200 mPa·s and the pH is 8.

[0033] Comparative Example This comparative example provides a facing paper-based material, which adopts conventional calendering and finishing methods.

[0034] Performance Testing Paper-based finishing materials were prepared using the soft calendering finishing methods of the paper-based finishing materials of Examples 1-3 and the comparative example, and the following tests were performed: Glossiness test: The glossiness of the paper-based finishing materials prepared by the soft calendering finishing method of the paper-based finishing materials of Examples 1-3 and the comparative example was tested using a gloss meter according to ISO 2813; Surface roughness test: The surface roughness of the paper-based finishing materials prepared by the soft calendering finishing method of the paper-based finishing materials of Examples 1-3 and the comparative example was tested using a PPS surface tester; Air permeability test: The air permeability of the paper-based finishing materials prepared by the soft calendering finishing method of the paper-based finishing materials of Examples 1-3 and the comparative example was tested using an air permeability tester according to ISO 5636-5; Water vapor transmission rate test: The water vapor transmission rate of the paper-based finishing materials prepared by the soft calendering finishing method of the paper-based finishing materials of Examples 1-3 and the comparative example was tested using a moisture permeability tester according to ISO 2528; The test results are shown in Table 1: Table 1 As can be seen from Table 1, the gloss, surface roughness, air permeability and water vapor permeability of the paper-based decorative materials prepared by the soft calendering finishing method of the paper-based decorative materials of Examples 1-3 are all better than those of the paper-based decorative materials prepared by the method of the comparative example, indicating that the paper-based decorative materials obtained by the soft calendering finishing method of the high-smoothness and high-permeability paper-based decorative materials of the present invention can simultaneously have high gloss, high smoothness and high air permeability; in particular, the paper-based decorative materials prepared by the soft calendering finishing method of the paper-based decorative materials of Examples 3 and 4 have better performance than those of Examples 1 and 2, which may be the effect of using more suitable process parameters and the preparation method of the inorganic filler coating liquid described in the present invention.

[0035] Throughout this specification, terms such as "one embodiment," "some embodiments," and "specific embodiments" mean that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0036] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A soft calendering finishing method for a highly smooth and breathable paper-based finishing material, characterized in that: include: S100, coating a paper base with an inorganic filler coating liquid to obtain a paper base with a coating; S200, pre-humidifying the coated paper base, and then soft-calendering the coated paper base with the assistance of steam to obtain a highly smooth and highly breathable paper-based finishing material; Wherein, the steam assistance is to spray the surface of the paper base with the coating with steam.

2. The soft calendering finishing method according to claim 1, characterized in that: After the pre-humidification treatment, the moisture content of the paper base with the coating is 7-10%.

3. The soft calendering finishing method according to claim 1, characterized in that: The steam used for the steam assistance comprises water vapor or liquid carbon dioxide; and / or The steam-assisted temperature is 30-50°C; and / or The roller temperature of the soft calendering treatment is 70-90°C.

4. The soft calendering finishing method according to claim 1, characterized in that: The preparation method further comprises: S300: After the soft calendering treatment, the coated paper base is subjected to a cooling and moisture removal treatment.

5. The soft calendering finishing method according to claim 4, characterized in that: The cooling and dehumidification treatment includes a water-cooled roller treatment or a negative pressure dehumidification treatment.

6. The soft calendering finishing method according to claim 1, characterized in that: The preparation method of the inorganic filler coating liquid comprises: S100, adding a dispersant to deionized water for a first stirring process, and adding an inorganic filler during the first stirring process to obtain an inorganic filler dispersion; S200 , performing a second stirring treatment on the inorganic filler dispersion, and sequentially adding acrylic-polyurethane emulsion and auxiliary agents during the second stirring treatment to obtain the inorganic filler coating liquid.

7. The soft calendering finishing method according to claim 6, characterized in that: The particle size of the inorganic filler is 1-3 μm.

8. The soft calendering finishing method according to claim 6, characterized in that: The rotation speed of the first stirring process is 1500-2000 rpm; and or The first stirring treatment lasts for 20-30 minutes; and / or The rotation speed of the second stirring process is 300-600 rpm; and / or The second stirring treatment lasts for 10-20 minutes.

9. The soft calendering finishing method according to claim 6, characterized in that: The inorganic filler comprises at least one of calcium carbonate, silicon dioxide and talc or a combination thereof; and / or The auxiliary agent includes at least one of a defoaming agent, a preservative, a thickener and a pH regulator, or a combination thereof.

10. The soft calendering finishing method according to any one of claims 6 to 9, characterized in that: The viscosity of the inorganic filler coating liquid is 1000-1200 mPa·s; and / or the pH of the inorganic filler coating liquid is 7-8.

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