Environment-friendly water-soluble chalk and preparation process thereof

Abstract

The invention provides an environment-friendly water-soluble chalk and a preparation process thereof, and the environment-friendly water-soluble chalk comprises the following components by weight: 50-65 parts of a water-soluble base material; 30 to 50 parts of solid filler; and 1-3 parts of a dispersant. The preparation process comprises the following steps: S1, putting a water-soluble base material into a stainless steel container in a constant-temperature oil bath, and continuously stirring by using a stirrer; s2, after the water-soluble base material is uniformly stirred, adding the solid filler and the dispersing agent, and continuously stirring by using the stirrer; and S3, after the material liquid is uniformly mixed and thickened into paste, pouring the material liquid into a chalk mold, and cooling and molding. According to the environment-friendly water-soluble chalk provided by the invention, a small amount of dispersing agent is added in the preparation process of the chalk, and the dispersing agent enables slurry to be thick to be pasty, so that solid filler is extremely difficult to precipitate at the bottom of the water-soluble slurry, the preparation requirement is greatly reduced, and the requirement on production equipment is low; and the production cost is reduced, and smooth writing of the chalk is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of teaching supplies, in particular to an environmentally friendly water-soluble chalk and a preparation process thereof. Background Art

[0002] At present, most schools use traditional chalk for teaching. The main components of traditional chalk are calcium carbonate, calcium sulfate, calcium oxide, as well as a small amount of metal elements and heavy metal elements such as lead, manganese, barium, cadmium, etc.

[0003] The plaster dust produced by traditional chalk writing easily becomes airborne. Long-term inhalation can cause respiratory illnesses such as pneumoconiosis and asthma, and can aggravate symptoms in those with allergies. Dust contact with skin or eyes can cause dryness, itching, or inflammation. Frequent use requires frequent hand washing, and erasing creates even more dust, potentially contaminating classroom equipment like projectors and electronic whiteboards.

[0004] Improved dust-free chalks have appeared on the market. These simply add grease and polyether surfactants to traditional chalk as binders, along with heavier raw materials. This increases the chalk's volume and specific gravity, making it less likely to scatter. However, this effect is not obvious during use, and a significant amount of dust is still produced during teaching. Furthermore, traditional chalk has a high coefficient of friction, making writing difficult and often fissures, making the written words less aesthetically pleasing.

[0005] To address these issues, a 100% dust-free water-soluble chalk has emerged in recent years. These chalks utilize a large number of water-soluble base materials, including but not limited to surfactants, fatty acids, waxes, amides, and a small amount of solid fillers, such as silica micropowder, talc, and titanium dioxide. While these chalks are 100% dust-free and harmless to humans and the environment, the large amount of liquid water-soluble base material added during their production requires the liquid base and solid filler to be uniformly stirred at high temperatures before being quickly poured into a mold and quenched to form the chalk before the solid filler settles. This production process places extremely high demands on stirring speed, stirring time, and quenching equipment, significantly increasing the production cost of the chalk. Furthermore, the water-soluble base and solid filler in existing water-soluble chalks are poorly dispersed, resulting in poor writing quality after the chalk is formed. This results in less-than-perfect whiteness, uneven texture, and cracked marks, which compromises the visual appeal of the chalk.

[0006] As shown in the Chinese invention patent application with publication number CN104109422 A, it discloses a water-soluble chalk for multimedia teaching and its preparation method, which includes a water-soluble base material and a solid filler. This technical solution is to make water-soluble chalk by quickly pouring the water-soluble base material and the solid filler into cold water for quenching after mixing them at high speed. However, there are still problems with this method. The solid filler with a larger specific gravity is very easy to precipitate at the bottom of the water-soluble base material during the material transfer and quenching process, resulting in uneven dispersion of the two types of raw materials in the chalk, which in turn affects the writing feel.

[0007] For example, Chinese invention patent application publication number CN108659626 A discloses a water-soluble chalk and a method for manufacturing the same. This method involves saponifying oil with an alkali to produce a slurry, adding a solid filler to the slurry, and then uniformly mixing the slurry and solid filler using high-speed grinding. However, this method requires high equipment requirements and a long preparation time, increasing the production cost of the chalk.

[0008] The following problems also exist in the prior art:

[0009] 1. Due to the presence of liquid water-soluble base materials and solid fillers in water-soluble chalk, the solid fillers are easily precipitated during the transfer and quenching of the evenly stirred slurry, resulting in uneven dispersion and affecting the writing effect of the chalk.

[0010] 2. If the slurry needs to be completely mixed and uniform without precipitation, the requirements for dispersion and quenching equipment and production time are extremely high, which increases the production cost of chalk. Summary of the Invention

[0011] The purpose of the present invention is to provide an environmentally friendly water-soluble chalk and a preparation process thereof, which can at least solve one of the above problems.

[0012] According to one aspect of the present invention, there is provided an environmentally friendly water-soluble chalk comprising the following components in parts by weight:

[0013] Water-soluble base, 50-65 parts;

[0014] Solid filler, 30-50 parts;

[0015] Dispersant, 1-3 parts.

[0016] In some embodiments, the water-soluble base includes four components: paraffin, polyether nonionic surfactant, stearic acid, and polyethylene glycol.

[0017] In some embodiments, the paraffin is 20-35 parts, the polyether nonionic surfactant is 8-20 parts, the stearic acid is 10-20 parts, and the polyethylene glycol is 3-10 parts.

[0018] In some embodiments, the paraffin is 28 parts, the polyether nonionic surfactant is 10 parts, the stearic acid is 15 parts, and the polyethylene glycol is 5 parts.

[0019] In some embodiments, the paraffin wax is 56# paraffin wax, the polyether nonionic surfactant is nonylphenol polyoxyethylene ether, and the polyethylene glycol is polyethylene glycol-400.

[0020] In some embodiments, the solid filler includes silica powder and titanium dioxide.

[0021] In some embodiments, the amount of silicon micropowder is 35-50 parts, and the amount of titanium dioxide is 1-3 parts.

[0022] In some embodiments, the dispersant is at least two of hydrophilic fumed silica, dispersant NNO, calcium stearate, and sodium carboxymethyl cellulose.

[0023] According to another aspect of the present invention, there is also provided a process for preparing an environmentally friendly water-soluble chalk, comprising the following steps:

[0024] S1. Place the water-soluble base material into a stainless steel container in a constant temperature oil bath, set the temperature to 100-120°C, and stir continuously for 10-20 minutes using a stirrer at a speed of 200-1000 rpm;

[0025] S2. After the water-soluble base is stirred evenly, add the solid filler and dispersant, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm;

[0026] S3. After the liquid material is mixed evenly and thickened to a paste, the liquid material is poured into a chalk mold and cooled and formed to obtain chalk.

[0027] Beneficial effects of the present invention:

[0028] 1. The present invention provides an environmentally friendly water-soluble chalk, in which a small amount of dispersant is added during the preparation process of the chalk. The dispersant makes the slurry viscous to a paste, making it extremely difficult for the solid filler to settle at the bottom of the water-soluble slurry. After the slurry is evenly mixed to a paste, it only needs to be poured into a chalk mold and wait for the chalk to be formed at room temperature. This has low requirements on production equipment, reduces production costs, and ensures that the chalk writing is silky and smooth.

[0029] 2. The preparation process of the present invention is simpler than that of conventional water-soluble chalk, does not require the use of quenching equipment, and does not require the entire process to rely on high-speed stirring and dispersing equipment for stirring, has low requirements on production equipment, and greatly reduces production costs;

[0030] 3. The water-soluble chalk of the present invention has smooth and silky writing properties, uniform handwriting texture, and good removability.

[0031] 4. The preparation process of the present invention does not discharge any wastewater or waste and does not pollute the environment.

[0032] 5. The water-soluble chalk of the present invention has a wide range of uses and is suitable for various boards.

[0033] 6. The present invention does not generate any dust when writing, is not harmful to the human body and the environment, and is environmentally friendly and pollution-free.

[0034] 7. The present invention has good weather resistance and can be used for writing at various temperatures. DETAILED DESCRIPTION

[0035] The present invention will be described in further detail below.

[0036] According to one aspect of the present invention, an environmentally friendly water-soluble chalk is provided.

[0037] The environmentally friendly water-soluble chalk comprises the following ingredients in parts by weight:

[0038] Water-soluble base, 50-65 parts;

[0039] Solid filler, 30-50 parts;

[0040] Dispersant, 1-3 parts.

[0041] Preferably, the water-soluble base comprises four components: paraffin, polyether nonionic surfactant, stearic acid and polyethylene glycol.

[0042] Preferably, the amount of paraffin wax is 20-35 parts, the amount of polyether nonionic surfactant is 8-20 parts, the amount of stearic acid is 10-20 parts, and the amount of polyethylene glycol is 3-10 parts.

[0043] As further preferred, the amount of paraffin is 28 parts, the amount of polyether nonionic surfactant is 10 parts, the amount of stearic acid is 15 parts, and the amount of polyethylene glycol is 5 parts.

[0044] As a further preference, the paraffin is 56# paraffin, the polyether nonionic surfactant is nonylphenol polyoxyethylene ether, and the polyethylene glycol is polyethylene glycol-400.

[0045] Among them, 56# paraffin was purchased from Shanghai Cunsi Industrial Co., Ltd.; stearic acid was purchased from Xilong Chemical Co., Ltd.; polyethylene glycol-400 and nonylphenol polyoxyethylene ether-9 were purchased from BASF GmbH, Germany.

[0046] The functions and effects of the components in the water-soluble base are as follows:

[0047] 1. Paraffin wax, stearic acid, and polyethylene glycol can significantly improve the lubrication properties of chalk writing, reduce the friction coefficient, make writing smoother, and reduce jamming and scratching. The long-chain alkane structure in these components can also enhance the structural hardness of chalk and reduce breakage and fragmentation.

[0048] 2. The hydrophobic particles of paraffin wax are dispersed in the base material to form a support network, which improves the compressive resistance and hardness of the chalk;

[0049] 3. The hydrophobicity of paraffin and stearic acid can slow down the dissolution rate of chalk when it comes into contact with water, so that it can maintain its temporary structural stability during writing. It can still be completely dissolved after being washed with water, thus preventing it from softening due to high humidity when not in use, preventing it from absorbing moisture and agglomerating, and increasing its weather resistance.

[0050] 4. Polyether nonionic surfactants as water-soluble base materials can increase writing lubricity and improve its erasability. The polyether nonionic surfactant uses nonylphenol polyoxyethylene ether-9, which has a high ethylene oxide number, making it more water-soluble and making the written words easier to wipe.

[0051] Preferably, the solid filler includes silica powder and titanium dioxide, wherein the silica powder mainly serves as a filler and the titanium dioxide mainly serves as a coloring agent.

[0052] Preferably, the amount of silicon micropowder is 35-50 parts and the amount of titanium dioxide is 1-3 parts.

[0053] As a further preferred embodiment, the silicon micropowder is 3000 mesh silicon micropowder, which can be purchased from Yangzhou Dilan Chemical Raw Materials Co., Ltd. Titanium dioxide is purchased from DuPont Inc. of the United States.

[0054] Preferably, the dispersant is at least two of hydrophilic fumed silica, dispersant NNO, calcium stearate, and sodium carboxymethyl cellulose. The addition of multiple dispersants further enhances the dispersibility of the inorganic filler and the oil-soluble base, allowing for complete and uniform mixing. This ensures smooth writing and reduces the equipment dependency of the water-soluble chalk preparation process.

[0055] As further preferred, the dispersant NNO was purchased from Qihua New Material Technology Co., Ltd., the hydrophilic fumed silica was purchased from Evonik Degussa, the calcium stearate was purchased from Luchuan Chemical Co., Ltd., and the sodium carboxymethyl cellulose was purchased from Chongqing Lihong Fine Chemical Co., Ltd.

[0056] According to another aspect of the present invention, a process for preparing an environmentally friendly water-soluble chalk is provided, comprising the following steps:

[0057] S1. Place the water-soluble base material into a stainless steel container in a constant temperature oil bath, set the temperature to 100-120°C, and stir continuously for 10-20 minutes using a stirrer at a speed of 200-1000 rpm;

[0058] S2. After the water-soluble base is stirred evenly, add the solid filler and dispersant, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm;

[0059] S3. After the liquid material is mixed evenly and thickened to a paste, the liquid material is poured into a chalk mold and cooled and formed to obtain chalk.

[0060] The present invention provides a new environmentally friendly water-soluble chalk and a preparation process, which has the following advantages:

[0061] 1. The present invention innovatively adds a small amount of dispersant during the chalk preparation process. The dispersant makes the slurry viscous to a paste, making it extremely difficult for the solid filler to settle at the bottom of the water-soluble slurry. After the slurry is evenly mixed to a paste, it only needs to be poured into a chalk mold and wait for the chalk to be prepared at room temperature. This has low requirements on production equipment, reduces production costs, and ensures that the chalk writing is silky and smooth.

[0062] 2. The preparation process of the present invention is simpler than that of conventional water-soluble chalk, does not require quenching equipment, has a short stirring time, a low rotation speed, and does not require high-speed stirring and dispersing equipment to be stirred throughout the entire process. It has low requirements on production equipment and greatly reduces production costs.

[0063] 3. Due to the combined effect of the water-soluble base and the dispersant, the water-soluble chalk of the present invention has smooth and silky writing and uniform handwriting texture, and has good removability due to the good water-soluble polyethylene glycol and polyether nonionic surfactant;

[0064] 4. The preparation process of the present invention does not discharge any wastewater or waste and does not pollute the environment;

[0065] 5. The water-soluble chalk of the present invention is suitable for various boards and has strong applicability and a wide range of uses;

[0066] 6. The invention does not generate any dust when writing, is not harmful to the human body and the environment, and is environmentally friendly and pollution-free;

[0067] 7. Since the present invention contains non-polar substances such as stearic acid and paraffin, the present invention has good weather resistance and can be used for writing at various temperatures.

[0068] The present invention is further described below by way of specific examples, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0069] Example 1

[0070] This embodiment provides an environmentally friendly water-soluble chalk, comprising the following components in parts by weight:

[0071] Water-soluble base, 58 parts;

[0072] solid filler, 41 parts;

[0073] Dispersant, 1 part.

[0074] The water-soluble base material is composed of the following components in parts by weight:

[0075] 56# paraffin wax, 28 parts;

[0076] Nonylphenol polyoxyethylene ether-9,10 parts;

[0077] Stearic acid, 15 parts;

[0078] Polyethylene glycol-400, 5 parts.

[0079] The solid filler is composed of the following components in parts by weight:

[0080] 3000 mesh silica powder, 39 parts;

[0081] Titanium dioxide, 2 parts;

[0082] The dispersant is composed of the following components in parts by weight:

[0083] Hydrophilic fumed silica, 0.5 parts;

[0084] 0.5 parts of calcium stearate.

[0085] This embodiment also provides a preparation process for an environmentally friendly water-soluble chalk. The environmentally friendly water-soluble chalk is prepared by the preparation process, which specifically includes the following steps:

[0086] S1. Place a water-soluble base consisting of 28 parts of 56# paraffin wax, 10 parts of nonylphenol polyoxyethylene ether-9, 15 parts of stearic acid, and 5 parts of polyethylene glycol-400 into a stainless steel container in a constant temperature oil bath, set the temperature to 100-120°C, and use a stirrer to continuously stir for 10-20 minutes at a stirring speed of 200-1000 rpm;

[0087] S2. After all the water-soluble base materials are stirred evenly, add 39 parts of 3000 mesh silica powder, 2 parts of titanium dioxide as a solid filler, and 0.5 parts of hydrophilic fumed silica and 0.5 parts of calcium stearate as a dispersant, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm;

[0088] S3, after the material liquid is mixed evenly and thickened to a paste, the material liquid is poured into a chalk mold, and after cooling and molding, the preparation is completed to obtain an environmentally friendly water-soluble chalk.

[0089] Example 2

[0090] This embodiment provides an environmentally friendly water-soluble chalk, comprising the following components in parts by weight:

[0091] Water-soluble base, 51 parts;

[0092] solid filler, 47.5 parts;

[0093] Dispersant, 1.5 parts.

[0094] The water-soluble base comprises the following components in parts by weight:

[0095] 56# paraffin wax, 22 parts;

[0096] Nonylphenol polyoxyethylene ether-9,9 parts;

[0097] Stearic acid, 12 parts;

[0098] Polyethylene glycol-400, 8 parts;

[0099] The solid filler comprises the following components in parts by weight:

[0100] 3000 mesh silica powder, 46 parts;

[0101] Titanium dioxide, 1.5 parts;

[0102] The dispersant includes the following components in parts by weight:

[0103] Hydrophilic fumed silica, 1 part;

[0104] Dispersant NNO, 0.5 parts.

[0105] This embodiment also provides a preparation process for an environmentally friendly water-soluble chalk. The environmentally friendly water-soluble chalk is prepared by the preparation process, which specifically includes the following steps:

[0106] S1. Place a water-soluble base consisting of 22 parts of 56# paraffin wax, 9 parts of nonylphenol polyoxyethylene ether-9, 12 parts of stearic acid, and 8 parts of polyethylene glycol-400 into a stainless steel container in a constant temperature oil bath, set the temperature to 100-120°C, and use a stirrer to continuously stir for 10-20 minutes at a stirring speed of 200-1000 rpm;

[0107] S2. After all the water-soluble base materials are stirred evenly, add a solid filler consisting of 46 parts of 3000 mesh silicon powder and 1.5 parts of titanium dioxide and a dispersant consisting of 1 part of hydrophilic fumed silica and 0.5 parts of dispersant NNO, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm;

[0108] S3, after the material liquid is mixed evenly and thickened to a paste, the material liquid is poured into a chalk mold, and after cooling and molding, the preparation is completed to obtain an environmentally friendly water-soluble chalk.

[0109] Example 3

[0110] This embodiment provides an environmentally friendly water-soluble chalk, comprising the following components in parts by weight:

[0111] Water-soluble base, 63 parts;

[0112] solid filler, 35 parts;

[0113] Dispersant, 2 parts.

[0114] The water-soluble base material includes the following components in parts by weight:

[0115] 56# paraffin wax, 32 parts;

[0116] Nonylphenol polyoxyethylene ether-9,11 parts;

[0117] stearic acid, 14 parts;

[0118] Macrogol-400, 6 parts;

[0119] The solid filler includes the following components in parts by weight:

[0120] 3000 mesh silica powder, 32 parts;

[0121] Titanium dioxide, 3 parts.

[0122] The dispersant includes the following components in parts by weight:

[0123] Sodium carboxymethyl cellulose, 1 part;

[0124] Dispersant NNO, 1 part.

[0125] This embodiment also provides a preparation process for an environmentally friendly water-soluble chalk. The environmentally friendly water-soluble chalk is prepared by the preparation process, which specifically includes the following steps:

[0126] S1. Place a water-soluble base consisting of 32 parts of 56# paraffin wax, 11 parts of nonylphenol polyoxyethylene ether-9, 14 parts of stearic acid, and 6 parts of polyethylene glycol-400 into a stainless steel container in a constant temperature oil bath. Set the temperature to 100-120°C and stir continuously for 10-20 minutes using a stirrer at a stirring speed of 200-1000 rpm.

[0127] S2. After all the water-soluble base materials are stirred evenly, add a solid filler consisting of 32 parts of 3000 mesh silicon powder, 3 parts of titanium dioxide, and a dispersant consisting of 1 part of sodium carboxymethyl cellulose and 1 part of dispersant NNO, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm.

[0128] S3, after the material liquid is mixed evenly and thickened to a paste, the material liquid is poured into a chalk mold, and after cooling and molding, the preparation is completed to obtain an environmentally friendly water-soluble chalk.

[0129] Example 4

[0130] This embodiment provides an environmentally friendly water-soluble chalk, comprising the following components in parts by weight:

[0131] Water-soluble base, 50 parts;

[0132] solid filler, 48 parts;

[0133] Dispersant, 2 parts.

[0134] The water-soluble base material includes the following components in parts by weight:

[0135] 56# paraffin wax, 20 parts;

[0136] Nonylphenol polyoxyethylene ether-9,17 parts;

[0137] Stearic acid, 10 parts;

[0138] Polyethylene glycol-400, 3 parts;

[0139] The solid filler includes the following components in parts by weight:

[0140] 3000 mesh silica powder, 47 parts;

[0141] Titanium dioxide, 1 part;

[0142] The dispersant includes the following components in parts by weight:

[0143] Sodium carboxymethyl cellulose, 1.2 parts;

[0144] Hydrophilic fumed silica, 0.8 parts.

[0145] This embodiment also provides a preparation process for an environmentally friendly water-soluble chalk. The environmentally friendly water-soluble chalk is prepared by the preparation process, which specifically includes the following steps:

[0146] S1. Place a water-soluble base consisting of 20 parts of 56# paraffin wax, 17 parts of nonylphenol polyoxyethylene ether-9, 10 parts of stearic acid, and 3 parts of polyethylene glycol-400 into a stainless steel container in a constant temperature oil bath. Set the temperature to 100-120°C and stir continuously for 10-20 minutes using a stirrer at a stirring speed of 200-1000 rpm.

[0147] S2. After all the water-soluble base materials are stirred evenly, add a solid filler consisting of 47 parts of 3000 mesh silica powder, 1 part of titanium dioxide, and a dispersant consisting of 1.2 parts of sodium carboxymethyl cellulose and 0.8 parts of dispersant NNO, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm.

[0148] S3, after the material liquid is mixed evenly and thickened to a paste, the material liquid is poured into a chalk mold, and after cooling and molding, the preparation is completed to obtain an environmentally friendly water-soluble chalk.

[0149] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. An environmentally friendly water-soluble chalk, characterized in that, The composition comprises the following components in parts by weight: Water-soluble base, 50-65 parts; Solid filler, 30-50 parts; Dispersant, 1-3 parts.

2. The environmentally friendly water-soluble chalk according to claim 1, wherein The water-soluble base material comprises four components: paraffin, polyether nonionic surfactant, stearic acid and polyethylene glycol.

3. The environmentally friendly water-soluble chalk according to claim 2, wherein The paraffin accounts for 20-35 parts, the polyether nonionic surfactant accounts for 8-20 parts, the stearic acid accounts for 10-20 parts, and the polyethylene glycol accounts for 3-10 parts.

4. The environmentally friendly water-soluble chalk according to claim 3, wherein The paraffin accounts for 28 parts, the polyether nonionic surfactant accounts for 10 parts, the stearic acid accounts for 15 parts, and the polyethylene glycol accounts for 5 parts.

5. The environmentally friendly water-soluble chalk according to any one of claims 2 to 4, characterized in that: The paraffin wax is 56# paraffin wax, the polyether nonionic surfactant is nonylphenol polyoxyethylene ether, and the polyethylene glycol is polyethylene glycol-400.

6. The environmentally friendly water-soluble chalk according to claim 1, characterized in that The solid filler includes silicon micropowder and titanium dioxide.

7. The environmentally friendly water-soluble chalk according to claim 6, characterized in that The silicon micropowder is 35-50 parts, and the titanium dioxide is 1-3 parts.

8. The environmentally friendly water-soluble chalk according to claim 1, characterized in that The dispersant is at least two of hydrophilic fumed silica, dispersant NNO, calcium stearate, and sodium carboxymethyl cellulose.

9. A process for preparing the environmentally friendly water-soluble chalk according to any one of claims 1 to 8, characterized in that: The steps include: S1. Place the water-soluble base material into a stainless steel container in a constant temperature oil bath, set the temperature to 100-120°C, and stir continuously for 10-20 minutes using a stirrer at a speed of 200-1000 rpm; S2. After the water-soluble base is stirred evenly, add the solid filler and dispersant, and continue stirring with a stirrer for 10-20 minutes at a stirring speed of 200-1000 rpm; S3. After the liquid material is mixed evenly and thickened to a paste, the liquid material is poured into a chalk mold and cooled and formed to obtain chalk.