CN108912807B - Method for improving wear resistance of waterborne polyurethane coating - Google Patents

Method for improving wear resistance of waterborne polyurethane coating Download PDF

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CN108912807B
CN108912807B CN201810940234.2A CN201810940234A CN108912807B CN 108912807 B CN108912807 B CN 108912807B CN 201810940234 A CN201810940234 A CN 201810940234A CN 108912807 B CN108912807 B CN 108912807B
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polyurethane coating
galactomannan
aqueous polyurethane
coating
wear resistance
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CN108912807A (en
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黄曹兴
勇强
吴燕
陶昱恒
杨磊
赖晨欢
李鑫
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Nanjing Forestry University
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Nanjing Forestry University
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    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09DCOATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40Additives
    • C09D7/60Additives non-macromolecular
    • C09D7/63Additives non-macromolecular organic
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09DCOATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04Polyurethanes

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Paints Or Removers (AREA)

Abstract

The invention discloses a method for improving the wear resistance of an aqueous polyurethane coating. 1% of the water-based paint is added, and the molecular weight range is 0.4 multiplied by 104~1.5×104The low molecular weight galactomannan of Da improves the wear resistance of the coating by 5.58-49.11%. The method for improving the wear resistance of the aqueous polyurethane coating has the advantages of simple process, easy control of conditions and good paint film performance, and can be widely applied to the fields of decoration, furniture, construction, machinery, chemical industry and the like.

Description

Method for improving wear resistance of waterborne polyurethane coating
Technical Field
The invention belongs to the technical field of environment-friendly coatings, and particularly relates to a method for improving the wear resistance of a waterborne polyurethane coating.
Background
The paint is a chemical mixture capable of being covered on the surface of an object firmly and used for protection, decoration, marking and other special purposes. The coating materials can be classified into organic solvent type coating materials, water-based coating materials, and the like according to the difference of solvents in the coating materials. Wherein, the dispersion medium of the solvent-based paint is an organic solvent, which plays a role in dissolving resin and diluting the paint. In the film-forming curing process of the solvent-based coating, after the organic solvent is volatilized, a film-forming substance is dried and formed into a film, so that a hard protective film is formed, and the effects of protecting and beautifying wood products and other substrates are achieved. The solvent-based paint mainly comprises volatile organic compounds such as benzene series, organic ketone, amine, alcohol, ether, ester, acid and the like, and the volatile organic compounds can generate a plurality of photochemical reactions under the action of sunlight to form secondary pollutants with higher toxicity, such as ozone, aldehydes, peroxyacetyl nitrate and the like. The special mixture composed of these nitrogen oxides, hydrocarbon compounds and their intermediate products of photochemical reaction is photochemical smog, and the generation of ozone is the sign of photochemical smog. Therefore, research and development of low pollution and environmental protection become a new direction for the development of the coating industry.
The water-based paint contains no or few volatile substances and air pollutants, has little harm to the environment and human health, and has become a research hotspot of green environment-friendly paints in the fields of furniture, buildings and the like. However, compared with the traditional solvent-based coating, the water-based coating has lower hardness and poorer wear resistance, and is not suitable for the fields of machinery, chemical engineering and the like with strong coating wear resistance. Therefore, the improvement of the wear resistance of the water-based paint is an important measure for improving the application field of the water-based paint in the paint industry.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defects of the prior art, the invention aims to provide a method for improving the wear resistance of an aqueous polyurethane coating, which uniformly disperses low-molecular-weight galactomannan with a certain molecular weight range in the aqueous coating and improves the wear resistance and the glossiness of the aqueous coating under the condition of not changing the hardness of the coating. The method has the advantages of simple process, easily controlled conditions and good paint film performance, and can be widely applied to the fields of decoration, furniture, construction, machinery, chemical industry and the like.
The technical scheme is as follows: in order to achieve the above object, the technical solution of the present invention is as follows:
a method for improving the wear resistance of aqueous polyurethane paint is characterized in that a galactomannan component is added into the aqueous polyurethane paint.
The addition amount of the galactomannan in g/mL is 1-3%.
The molecular weight range of the galactomannan is 0.4 × 104~1.5×104Da。
The molecular weight range of the galactomannan is 1.5 × 104Da。
The method for improving the wear resistance of the aqueous polyurethane coating comprises the steps of adding the galactomannan component before the aqueous polyurethane coating is used, and uniformly mixing.
According to the method for improving the wear resistance of the aqueous polyurethane coating, every 100mL of the aqueous polyurethane coating contains 71.4mL of polyurethane polyhydroxy prepolymer dispersion liquid and 28.6mL of polyisocyanate curing agent.
Galactomannan (GM) is a nonlinear heteropolysaccharide which takes mannose as a basic structural unit and forms a main chain through beta-1, 4-glycosidic bonds, and galactose is connected to the main chain through alpha-1, 6-glycosidic bonds, and has the characteristics of acid and alkali resistance, good thermal stability, high molecular weight, high viscosity, high hydroxyl content, strong water solubility and the like. According to the application, the galactomannan is uniformly dispersed in the coating, rich hydroxyl in the polysaccharide can be in hydrogen bond combination with alcoholic hydroxyl of polyhydric alcohol in the water-based coating, and the galactomannan and the coating are crosslinked to form a compound, so that the water-based coating is endowed with some special properties.
Has the advantages that: compared with the prior art, the galactomannan with a certain molecular weight range is added into the waterborne polyurethane coating, so that the wear resistance of the waterborne coating can be effectively improved under the condition of not changing the hardness of the coating. The method has the advantages of simple process, easily controlled conditions and good paint film performance, and can be widely applied to the fields of decoration, furniture, construction, machinery, chemical industry and the like.
Detailed Description
The invention is further illustrated by the following examples. The examples are intended to illustrate, but not to limit, the invention. Those of ordinary skill in the art will understand that these examples are not intended to limit the present invention in any way, and that appropriate modifications can be made without departing from the spirit and scope of the present invention.
In the following examples, galactomannan molecular weights (Mw) were determined by HPLC. Chromatograph: HPLC high performance liquid chromatograph; a chromatographic column: three columns, namely a Waters Ultrahydrogel TM 2000 (7.8X 300mm), a Waters Ultrahydrogel TM 250 (7.8X 300mm) and a Waters Ultrahydrogel TM 120 (7.8X 300mm), are connected in series in sequence; mobile phase: ionized water with the flow rate of 0.6 mL/min; column temperature: 65 ℃; detecting by a difference detector; standard samples: polyethylene glycol (molecular weight 360-120000 Da).
Example 1
Preparation method of low molecular weight galactomannan
(1) Galactomannan extract preparation. Mechanically pulverizing air-dried sesbania endosperm sheet, adding distilled water at a solid-liquid ratio of 1: 50, extracting at 50 deg.C for 24 hr, centrifuging at 10000 rpm for 10min to obtain supernatant, adding anhydrous ethanol into the supernatant to obtain precipitate, and vacuum drying the precipitate to obtain galactomannan powder.
(2) The endo-mannanase selectively hydrolyzes galactomannans. Weighing 20.0g of the galactomannan extract obtained in the step (1) into a 2L enzyme reaction tank, adding distilled water, endo-mannase and 1mol/L citric acid buffer solution to enable the volume of reaction liquid to be 1000mL, fully and uniformly mixing, reacting for 24h under the conditions of substrate concentration of 10%, enzyme addition of 20U/g galactomannan, pH value of 4.8 and 50 ℃, after the enzymatic hydrolysis reaction is finished, placing an enzymatic hydrolysate at 100 ℃ for 10min to inactivate the endo-mannase, centrifuging for 10min under the condition of 10000 r/min, and obtaining supernatant which is the enzymatic hydrolysate containing the incomplete degradation product of the galactomannan.
(3) Low molecular weight galactomannan fractions of various molecular weight ranges were prepared. And (3) taking 1000mL of galactomannan enzymolysis supernatant in the step (2), adding absolute ethyl alcohol under the stirring condition to ensure that the concentration of the ethyl alcohol in the system is 40% (v/v), and centrifuging for 10min under the condition of 10000 r/min to obtain supernatant and precipitate. The precipitate was washed 3 times with 30mL of 40% (v/v) aqueous ethanol, centrifuged (10000 rpm, 10min), freeze-dried to give a solid sample P1, and its molecular weight was measured. The supernatant was used for further fractionation in the next stage.
(4) And (4) taking the supernatant obtained after the solid-liquid separation in the step (3), adding absolute ethyl alcohol under the stirring condition to ensure that the concentration of the ethyl alcohol in the system is 50% (v/v), and centrifuging for 10min under the condition of 10000 r/min to obtain the supernatant and the precipitate. The precipitate was washed 3 times with 30mL of 50% (v/v) aqueous ethanol, centrifuged (10000 rpm, 10min), freeze-dried to give a solid sample P2, and its molecular weight was measured. The supernatant was used for further fractionation in the next stage.
(5) And (4) taking the supernatant obtained after the solid-liquid separation in the step (4), adding absolute ethyl alcohol under the stirring condition to ensure that the concentration of the ethyl alcohol in the system is 65% (v/v), and centrifuging for 10min under the condition of 10000 r/min to obtain the supernatant and the precipitate. The precipitate was washed 3 times with 30mL of a 65% (v/v) aqueous ethanol solution, centrifuged (10000 rpm, 10min), freeze-dried to give a solid sample P3, and its molecular weight was measured.
The results showed that the obtained low molecular weight galactomannans P1, P2 and P3 of different molecular weights had molecular weights of 1.5X 104Da、0.8×104Da and 0.4X 104Da。
Example 2
The preparation of the high-wear-resistance waterborne polyurethane coating comprises the following steps
(1) A commercially available polyurethane polyhydroxy prepolymer dispersion liquid (solid content is 40%, w/v) and a polyisocyanate curing agent (solid content is 80%, w/v) were weighed out, 71.4mL of polyurethane polyhydroxy prepolymer dispersion liquid and 28.6mL of polyisocyanate curing agent were weighed out according to a ratio of 10: 4 (v: v) of prepolymer dispersion liquid to curing agent, and dispersed for 10min at 25 ℃ by a homogenizer to obtain an aqueous polyurethane coating.
(2) And (2) adding 1g, 2g and 3g of galactomannan (P1, P2 and P3) with different molecular weights as a modifier into 100mL of the aqueous polyurethane coating obtained in the step (1) according to the addition amount of the low molecular weight galactomannan of 1%, 2% and 3%, and dispersing for 10min at 25 ℃ by using a homogenizer to obtain the modified aqueous polyurethane coating.
Example 3
The aqueous polyurethane coating and the modified polyurethane coating prepared in example 2 were applied to the surface of a wood substrate by pressure spraying. The wood substrate used was a multilayer plywood with a size of 10X 10cm and a coating thickness of 60 μm. After the coating on the surface of the wood substrate is solidified into a film, the substrate is placed in a 50 ℃ forced air drying oven to be dried for 120min to evaporate redundant moisture in the coating, and after the substrate is placed in a ventilation mode at room temperature for 7d, the adhesion, the glossiness, the abrasion loss and the pencil hardness are detected.
The performance results of the aqueous polyurethane coating and the modified aqueous polyurethane coating are shown in table 1.
TABLE 1 Properties of aqueous polyurethane coating and modified aqueous polyurethane coating
Numbering Addition amount (%) Grade of adhesion Hardness of pencil Amount of wear (g) Abrasion resistance increasing rate (%)
Water-based paint 0 2 5H 0.0167 -
P1+ Water-based paint 1 2 5H 0.0085 49.11
P1+ Water-based paint 2 2 5H 0.0091 45.51
PI + water paint 3 2 5H 0.0104 37.72
P2+ Water-based paint 1 2 5H 0.0103 38.32
P2+ Water-based paint 2 2 5H 0.0105 37.13
P2+ Water-based paint 3 2 4H 0.0117 29.94
P3+ Water-based paint 1 2 5H 0.0151 9.58
P3+ Water-based paint 2 2 4H 0.0155 7.19
P3+ Water-based paint 3 2 4H 0.0161 3.59
The result shows that the addition of the low molecular weight galactomannan modifier with different molecular weights in the waterborne polyurethane coating does not change the adhesion capability of the coating on a wood substrate and the hardness of the coating. When the addition amount is 1%, the molecular weight is 1.5X 104Da、0.8×104Da and 0.4X 104With Da of low molecular weight galactomannan, the abrasion resistance of the water paint is improved by 49.11%, 38.32% and 9.58%, respectively, which shows that the galactomannan as a modifier of the water paint can improve the abrasion resistance.

Claims (4)

1. A method for improving the wear resistance of aqueous polyurethane paint is characterized by comprising the following steps: the aqueous polyurethane coating is added with a galactomannan component; the addition amount of the galactomannan is 1-3 g/100mL, and the molecular weight of the galactomannan is 0.8 multiplied by 104Da ~1.5×104Da。
2. The method of claim 1, wherein the galactomannan has a molecular weight in the range of 1.5 x 104Da。
3. The method for improving the abrasion resistance of the aqueous polyurethane coating according to claim 1, wherein the galactomannan component is added and mixed uniformly before the aqueous polyurethane coating is used.
4. The method for improving the abrasion resistance of an aqueous polyurethane coating according to claim 1, wherein the aqueous polyurethane coating contains 71.4mL of the polyurethane polyhydroxy prepolymer dispersion and 28.6mL of the polyisocyanate curing agent per 100mL of the aqueous polyurethane coating.
CN201810940234.2A 2018-08-16 2018-08-16 Method for improving wear resistance of waterborne polyurethane coating Active CN108912807B (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101348530A (en) * 2008-09-17 2009-01-21 北京林业大学 Galactomannan gum got by irradiation degradation, preparation and use thereof
CN104761940A (en) * 2015-03-25 2015-07-08 田福东 Wear-resistant waterborne polyurethane coating

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101348530A (en) * 2008-09-17 2009-01-21 北京林业大学 Galactomannan gum got by irradiation degradation, preparation and use thereof
CN104761940A (en) * 2015-03-25 2015-07-08 田福东 Wear-resistant waterborne polyurethane coating

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
纳米纤维素改性水性聚氨酯及其在木器涂料中的应用;潘汝潭;《中国优秀硕士学位论文全文数据库 工程科技Ⅰ辑》;20180115(第1期);正文第7-8,24-26、33-35页 *

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