CN113736294A

CN113736294A - Inorganic binder suitable for automobile coating and preparation method thereof

Info

Publication number: CN113736294A
Application number: CN202010460417.1A
Authority: CN
Inventors: 代忠祥; 刘扬; 邱绍义; 叶东明; 刘艳平
Original assignee: Langfang Nippon Paint Co ltd
Current assignee: Langfang Nippon Paint Co ltd
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2021-12-03
Anticipated expiration: 2040-05-27
Also published as: CN113736294B

Abstract

The invention discloses an inorganic binder suitable for automobile paint, which comprises the following raw materials, by weight, 90-98 parts of a solvent, 1-5 parts of sheet silicate and 0.1-5 parts of polypropylene glycol; the gel time of the sheet silicate is 0-2min, and the gel strength is 22-52g/cm². The inorganic binder has better high-pressure shearing resistance and orientation to metal pigment, so that the color of the paint is not changed after high-pressure shearing, and the color stability among batches is ensured. Meanwhile, the inorganic adhesive can be directly added into the coating during high-speed dispersion, so that the production efficiency is improved.

Description

Inorganic binder suitable for automobile coating and preparation method thereof

Technical Field

The invention relates to the field of binder preparation. More particularly, it relates to an inorganic binder suitable for automotive coatings and a method for preparing the same.

Background

The proportion of the metal pigment in the current automobile coating system is higher, accounting for 5-7% of the total formula amount, and is close to the upper limit range of formula design, and the requirements on the type and the use amount of the binder in the coating system are higher. In the prior art, the organic polymer material used as a binder has larger molecular weight and longer molecular chain, and has better fixation on organic and inorganic pigments in a system in a standing state or a low-shear state; however, when the coating system is subjected to high pressure and long-term high shear force cycling, the binding capacity of the existing organic polymer binder is reduced, and the fixing effect on the metal pigment is weakened. When the system is subjected to high-pressure shearing, the orientation of the metal pigment is changed, the metal pigment is more obvious after three days, the brightness of 15 degrees is reduced by 9-10 points, and the brightness of 45 degrees, 75 degrees and 110 degrees are increased by 3-6 points, which are beyond the control range of product design.

Under some use conditions, the demand of the coating with high metal pigment content is low, the replacement frequency of the coating in a circulating pipeline is low, the circulation time of a single batch of coating in the pipeline is prolonged, the time of the coating subjected to high-pressure shearing force of a circulating pump is prolonged, the directionality of the organic binder to the metal pigment is weakened, the viscosity of the coating is changed in the circulation process, and the color of the coating is changed, so that the color index of the single batch of coating exceeds the color control range after the single batch of coating is put into the circulating pipeline for three days, the field color is abnormal, the vehicle can not be handed over on time due to the fact that the color does not reach the standard, and the complaint of some customers is caused.

Along with the improvement of living standard, consumers have higher requirements on the color of the automobile, and meanwhile, the control strength of automobile manufacturers on the color is increasingly strengthened, so that the requirements of paint manufacturers on the color stability of paint products are higher and stricter, the stability of the products can be ensured, the color of the products is not changed after the products are sheared under high pressure, and the color stability among batches is ensured. In order to maintain the color stability of the product, the existing binder can not be kept stable under a high shearing force for a long time and can not meet the requirement of a customer on the color stability, so that the development of an inorganic binder with good cyclic shearing resistance for the application in an automobile coating is needed.

Disclosure of Invention

An object of the present invention is to provide an inorganic binder suitable for automotive coatings, which has better high shear resistance and orientation to metallic pigments, and can be directly added into high-speed dispersion coatings, thereby simplifying the process while ensuring the viscosity stability of the coatings.

Another object of the present invention is to provide a method for preparing an inorganic binder suitable for use in automotive coatings.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides an inorganic binder suitable for automobile coatings, which comprises 90-98 parts by weight of solvent, 1-5 parts by weight of sheet silicate and 0.1-5 parts by weight of polypropylene glycol;

the gel time of the sheet silicate is 0-2min, and the gel strength is 22-52g/cm²。

Optionally, the sheet silicate has a sheet structure, a sheet diameter of 20-30 nm, and a thickness of 0.8-1.1 nm.

Optionally, the sheet silicate is lithium magnesium silicate.

Optionally, the hydroxyl value of the polypropylene glycol is 107-117 mgKOH/g, the acid value is 0-0.05 mgKOH/g, and the number average molecular weight is 1000. ltoreq. M.ltoreq.1500.

Optionally, the solvent is deionized water. It is feasible to prepare the inorganic binder, but mineral water and tap water, because they contain an ionic substance, form a highly thixotropic gel in a short time after the preparation of the inorganic binder, resulting in binder failure, and cannot achieve the effect of improving the viscosity and thixotropy of the paint after being added to the paint.

Optionally, the inorganic binder has a wet film fineness of 5 μm or less.

In a second aspect, the present invention provides a method for preparing an inorganic binder suitable for automotive coatings, comprising the steps of:

slowly adding the sheet silicate into the solvent under stirring at a linear speed of more than or equal to 4 m/s, and then continuously stirring; and continuously adding the polypropylene glycol, and uniformly stirring and dispersing to obtain the polypropylene glycol.

Optionally, the preparation method of the inorganic binder further comprises a detection process, namely adding 1% DMEA into the stably dispersed inorganic binder, uniformly stirring, then visually clarifying and transparent, and detecting the fineness of the solution.

Alternatively, the addition rate of the sheet silicate to the solvent is from 1 to 1.5 kg/min.

Optionally, the temperature of the solvent is 18-25 ℃.

The invention has the following beneficial effects:

the invention provides an inorganic binder suitable for automobile paint, which has better high-pressure shearing resistance and orientation to metal pigment than the current polyurethane adhesive and acrylic adhesive used for automobile finish paint, so that the color of the paint does not change after high-pressure shearing, and the color stability among batches is ensured. Meanwhile, the inorganic adhesive can be directly added into the coating during high-speed dispersion, and does not need to be added when the stirring is reduced or stopped like the existing polyurethane and acrylic adhesive, so that the material adding process is simplified, and the production efficiency is improved.

Detailed Description

In order to make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail with reference to specific embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

In the case where the objects of the present invention are illustrated and explained by the following examples, the components of the composition are all explained on the general standard of parts by weight. In the present invention, the term "part" is used in the same sense as part by weight for the sake of brevity without specific mention.

In the prior art, the binder used in the automobile paint is generally an organic binder such as a polyurethane binder, an acrylic acid type binder and the like, and the orientation effect of the binder on the metal pigment is weakened under the action of long time and high shear force, so that the color of the paint is changed, and the painting result is not ideal. Meanwhile, in order to avoid the influence of high shearing force on the organic binder, the organic binder needs to be added under low shearing force or static state, so that the process is complicated, and the production efficiency is influenced.

Aiming at the problems in the prior art, the invention provides an inorganic binder suitable for automobile paint, which comprises the following raw materials, by weight, 90-98 parts of a solvent, 1-5 parts of sheet silicate and 0.1-5 parts of polypropylene glycol;

The sheet silicates in the inorganic binder provided by the present invention have rheological properties including: 1. high viscosity at low shear; 2. low viscosity at high shear; 3. fast shear thinning; 4. the thixotropic structure recovers quickly and controllably after shearing. The rheological property is beneficial to maintaining the stability of the binder under long-time high shearing force, so that the color of the coating is not changed after high-pressure shearing, and the color stability among batches is ensured.

One possible realization way is that the sheet silicate has a sheet structure, the sheet diameter of the sheet silicate is 20-30 nm, and the thickness of the sheet silicate is 0.8-1.1 nm. The platelets disperse in water to form platelet crystals, which can be considered as two-dimensional "inorganic polymers".

In a preferred example, the sheet silicate is lithium magnesium silicate. The single unit cell in a lithium magnesium silicate crystal comprises 6 octahedral structures, with magnesium ions sandwiched between two layers of 4 tetrahedral silicon atoms, these groups being charge balanced by 20 oxygen atoms and 4 hydroxyl groups. The height of the unit cell determines the thickness of the crystal. The unit cell is repeated a plurality of times in two dimensions to form a wafer. A typical plate silicate crystal contains up to 2000 unit cells. The preparation process of the lithium magnesium silicate comprises the following steps: mixing sodium ions, magnesium ions, lithium salt and sodium silicate at a certain speed and temperature to generate amorphous precipitate, forming partial crystal through high-temperature treatment, and then filtering, washing, drying and grinding to obtain fine lithium magnesium silicate powder.

The inorganic binder provided by the invention does not contain organic high molecular materials, and comprises a solvent, sheet silicate and polypropylene glycol. The front and sides of the lithium magnesium silicate sheet silicate are oppositely charged, electrostatic attraction pulls sodium ions in solution to the crystal surface, and osmotic pressure of water molecules tends to separate the sodium ions. Sodium ions establish balance in diffusion regions on the front and back sides of the dispersed crystals, when the two crystals are close to each other, positive charges of the two crystals are mutually repelled, and the dispersion liquid has low viscosity and Newtonian flow. The addition of an active material such as polypropylene glycol to the inorganic binder dispersion reduces the osmotic pressure that repels sodium ions on the crystal surface, resulting in shrinkage of the electric double layer, the weak positive charges at the crystal edges interact with the negative charges on the adjacent crystal surfaces, and this process continues to develop to form a "cabin" structure, with the gel being held together by the positive and negative charge attractions of the crystals.

The formed 'cabin' structure is characterized in that: 1, the metal pigment can be stabilized in a three-dimensional gel structure, is prevented from sinking by relying on viscosity, and has excellent suspensibility on the metal pigment with overlarge density; 2, based on acting force between charges, the viscosity of the system is not influenced by temperature; 3, the gel structure is easy to break by shearing force, and the inorganic binder shows stronger shear thinning state than the organic binder; 4, under high shearing force, the viscosity of the inorganic binder is low, and the flow is not influenced; and 5, after the shearing force is removed, the crystal is reoriented to form a cabin structure in a short time. Thereby improving the high-pressure shearing resistance of the system.

The invention also provides a possible preparation method of the sheet silicate solution, which is to slowly add the powdery silicate into water during stirring and then continue stirring until the powdery silicate is fully dispersed in the water.

The polypropylene glycol facilitates dispersion of the sheet silicate in a solvent and maintains stability after dispersion. In a preferred embodiment, the polypropylene glycol has a hydroxyl value of 107 to 117mgKOH/g, an acid value of 0 to 0.05mgKOH/g, and a number average molecular weight in the range of 1000. ltoreq. M.ltoreq.1500.

One possible implementation is that the solvent is deionized water. Since mineral water and tap water contain an ionic substance, a highly thixotropic gel is formed in a short time after the inorganic binder is prepared, so that the binder loses efficacy, and the effect of improving the viscosity and thixotropy of the coating cannot be achieved after the inorganic binder is added into the coating.

One possible realization is that the wet film fineness of the inorganic binder is 5 μm or less.

The invention also provides a possible preparation method of the inorganic binder suitable for the automobile coating, which comprises the following steps:

adding the sheet silicate into the solvent under stirring at a linear speed of more than or equal to 4 m/s, and then continuing stirring; and continuously adding the polypropylene glycol, and uniformly stirring and dispersing to obtain the polypropylene glycol.

After the preparation, the inorganic binder with stable dispersion is taken, 1% of DMEA is added into the inorganic binder, the mixture is stirred uniformly, the mixture is clarified and transparent visually, and the fineness of a wet film is detected.

The sheet silicate is a white solid powder during the preparation process, and when it is added to the solvent, it must be slowly added during stirring, and preferably, the addition rate is 1 to 1.5 kg/min. If the addition is too fast, the sheet silicate aggregates and agglomerates are not easily dispersed, and if the gel is seriously precipitated, the performance of the adhesive is reduced and the normal adhesive effect cannot be exerted even if the sheet silicate is continuously dispersed until no obvious insoluble substance is observed visually. In addition, the temperature of the solvent is 18-25 ℃ in the specific preparation process.

To illustrate the ability of the inorganic binder suitable for automotive coatings provided by the present invention in terms of resistance to cyclic shear, the specific process can be verified by corresponding tests, and is as follows:

the binder provided by the invention is put into finish paint to prepare coating, then one part of the coating is left and placed, the other part of the coating is put into a circulating pipe (model: GRACO E-flo DC), and after continuous circulation for 3 days, the circulating conditions are shown in Table 1:

TABLE 1 circulation conditions

After the circulation is finished, the sample retention paint and the circulated paint are subjected to brightness test under the same process conditions.

The technical solution protected by the present invention will be described with reference to some specific embodiments.

Preparation example

Preparation of inorganic Binder

The preparation method of the inorganic binder comprises the following steps:

slowly adding the sheet silicate into the solvent under stirring at a linear speed of more than or equal to 4 m/s, and then stirring for 60 min; and continuously adding polypropylene glycol, and uniformly stirring and dispersing to obtain the inorganic binder.

Adding 1% DMEA into the inorganic binder, uniformly stirring, visually clarifying and transparent, and detecting the fineness of a wet film.

Preparation examples 1 to 3

The raw material compositions of the inorganic binders in preparation examples 1 to 3 are shown in Table 2

TABLE 2 raw material composition of inorganic Binder in preparation examples 1 to 3

Raw material classification	Name of raw materials	Preparation example 1/part	Preparation example 2 parts by weight	Preparation example 3 parts by weight
					Solvent(s)	Deionized water	96	97	98
Sheet silicate	LAPONITE RD	3	2	1
					Polypropylene glycol	PPG1000	1	1	1

The lithium magnesium silicate LAPONITE RD has a gel time of 0-2min and good stability.

Preparation examples 4 to 6

The raw material compositions of preparation examples 4 to 6 are shown in Table 3.

TABLE 3 raw material composition of inorganic Binders in preparation examples 4 to 6

The lithium magnesium silicate LAPONITE EP of preparation example 4 had a gel time of 0 to 6min, a relatively long gel time and relatively poor stability, which resulted in a long gel time, poor orientation to metallic pigments and a reduced F/F property of the coating. The lithium magnesium silicate Hatoreite RD from preparation 5 has a gel time of 0 to 6 minutes, a relatively long gel time, poor stability, a long gel time, poor orientation to metallic pigments, and a reduced F/F of the coating. The lithium magnesium silicate Baiyike YK-200 in preparation example 6 has a gel time of 0-8min, a wide gel time and poor stability. This results in a long gel time, poor orientation to the metallic pigment and a decrease in the F/F properties of the coating.

Preparation examples 7 to 9

The raw material compositions of the inorganic binders in preparation examples 7 to 9 are shown in Table 4

TABLE 4 raw material compositions of inorganic binders in preparation examples 7 to 9

The number average molecular weight of the polypropylene glycol added in preparation examples 7 to 9 did not meet the requirement that the molecular weight was within the range of 1000-1500, thereby affecting the dispersion of the sheet silicate in the solvent and maintaining the stability after dispersion.

Examples

Preparation method of automobile coating

Adding polyurethane resin, acrylic emulsion, polyester resin, a surface modifier and amino resin into the container 1, stirring uniformly, adding a bonding auxiliary agent, and stirring uniformly at a high speed until the fineness meets the requirement; adding other additives and pure water for uniform dispersion;

adding a solvent and a metal pigment into the container 2, adding the phosphate resin under the stirring state, and uniformly dispersing;

and mixing the substances in the container 2 and the substances in the container 1, adding an inorganic binder, and adjusting the viscosity of the coating to obtain the automobile coating.

Examples 1 to 3

The raw material compositions of the automotive coatings of examples 1-3 are shown in Table 5, wherein the inorganic binder prepared in preparation example 1 was added in example 1; example 2 the inorganic binder prepared in preparation example 2 was added; in example 3, the inorganic binder prepared in preparation example 3 was added.

Comparative examples 1 to 6

The raw material compositions of the automotive coatings in comparative examples 1 to 3 are shown in table 5, wherein in comparative example 1, the inorganic binder prepared in preparation example 4 was added; in comparative example 2, the inorganic binder prepared in preparation example 5 was added; the inorganic binder prepared in preparation example 6 was added in comparative example 3, and the inorganic binder prepared in preparation example 7 was added in comparative example 4; comparative example 5 was added the inorganic binder obtained in preparation example 8; in comparative example 6, the inorganic binder obtained in preparation example 9 was added.

TABLE 5 raw material compositions of automotive coatings in examples 1 to 3 and comparative examples 1 to 3

In Table 5, the adhesion promoter is one or more selected from RHEOVIS AS 1130 promoter, ADEKANOL UH-814N, BYK-425, BYK-420 and DeuRhpeo 102; the surface modifier is one or more of SURFYNOL104PA, SURFYNOL420, SURFYNOL440, SURFYNOL465 and SURFYNOL DF-37; the other additive is at least one of a flatting agent, a dispersing agent, a defoaming agent, a preservative and a light stabilizer; the solvent is one or more selected from ethylene glycol butyl ether, propylene glycol butyl ether, isooctanol, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, ethylene glycol isopropyl ether, diacetone alcohol and ethanol.

The solid content of the obtained automobile coating is 24-25%, and the PWC of the metal pigment is 14-16%.

Test example

The coatings prepared in examples 1 to 3 and comparative examples 1 to 6 were introduced into a circulation line (model: GRACO E-flo DC) and continuously circulated for 72 hours under the circulation conditions shown in Table 6

TABLE 6 Recycling conditions for the coatings prepared in examples 1-3 and comparative examples 1-6

Main pump type	GRACO E-flo DC
		Main pump material	Stainless steel
Pressure ratio of main pump	3：1
		Output flow of main pump	750 ml
System output flow rate fluctuation range	Less than 50 ml/min
		Flow rate of system circulation	9 to 18 m/s
System circulation pressure	3～12KG
		System cyclic pressure fluctuation range	Less than 1KG
System paint supply pressure	10～12KG
		Circulating back pressure	4～6KG
Pipe diameter mm	20
		Length of pipe m	18
Pump frequency/minute (one round trip)	8.5
		Flow rate L/times	1.5
Total amount of recycled coating/L	25

After the cycle is over, the test will be performed under the following process:

spraying the paint which is not circulated and the paint which is circulated for 72 hours on a dark grey middle coating board, leveling for 3 minutes, pre-baking for 5 minutes at 80 ℃, spraying MAC O-1860 varnish, leveling for 5 minutes, baking at 140 ℃ for 20 minutes, taking out to room temperature, and testing by using a MA68II multi-angle color difference meter.

The results obtained are shown in tables 7, 8 and 9:

TABLE 7 color and Change before and after coating cycling in examples 1-3

Note: in Table 7, OK indicates "pass", NG indicates "fail

TABLE 8 color and Change before and after coating cycling in comparative examples 1-3

Note: in Table 8, OK indicates "pass", NG indicates "fail"

TABLE 9 color and Change before and after coating cycle in comparative examples 4-6

Note: in Table 9, OK indicates "pass", NG indicates "fail

Since the sheet silicate in the inorganic binder used in comparative examples 1 to 3 did not satisfy the requirements, the high pressure cycle discoloration resistance of the coating material was not satisfied.

Since the polypropylene glycol in the inorganic binder used in comparative examples 4 to 6 did not satisfy the requirements, the high pressure cycle discoloration resistance of the coating material was not satisfied.

The invention also examined other properties of the paint films of examples 1-3 and comparative examples 1-6, the results of which are shown in tables 10 and 11:

TABLE 10 other Properties of the paint films in examples 1 to 3 and comparative examples 1 to 3

TABLE 11 further Properties of the paint films of comparative examples 4 to 6

The results in tables 10 and 11 show that the other properties of the paint film are not affected and still meet the requirements after the inorganic binder provided by the present invention is added.

The use of an inorganic adhesive for the aqueous polymer material improves the high pressure cycle discoloration resistance of the metallic aqueous polymer material, but if an unspecified solvent, inorganic binder or PPG having a number average molecular weight within a range required is used, the above-mentioned effects are not obtained.

The experimental scheme is applied to batch production, can reach expectation, meets the requirement that the product is continuously circulated in a pipeline and is not discolored due to no production for a long time, and is qualified in performances such as coating appearance, sagging property and the like.

It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims

1. The inorganic binder suitable for the automobile coating is characterized by comprising 90-98 parts of solvent, 1-5 parts of sheet silicate and 0.1-5 parts of polypropylene glycol;

2. The inorganic binder as claimed in claim 1, wherein the sheet silicate has a sheet structure, a sheet diameter of 20 to 30nm, and a thickness of 0.8 to 1.1 nm.

3. The inorganic binder according to claim 1, wherein the sheet silicate is lithium magnesium silicate.

4. The inorganic binder as claimed in claim 1, wherein the polypropylene glycol has a hydroxyl value of 107 to 117mgKOH/g, an acid value of 0 to 0.05mgKOH/g, and a number average molecular weight of 1000. ltoreq. M.ltoreq.1500.

5. The inorganic binder of claim 1, wherein the solvent is deionized water.

6. The inorganic binder as claimed in claim 1, wherein the inorganic binder has a wet film fineness of 5 μm or less.

7. A method for preparing an inorganic binder suitable for use in automotive coatings according to claim 1, characterized by comprising the steps of:

slowly adding the sheet silicate into the solvent under stirring at a linear speed of more than or equal to 4 m/s, and then stirring; and continuously adding the polypropylene glycol, and uniformly stirring and dispersing to obtain the polypropylene glycol.

8. The method of claim 7, wherein the method further comprises a step of measuring the fineness of the wet film by adding 1% DMEA to the inorganic binder with stable dispersion, stirring the mixture uniformly, and then visually observing the mixture to be clear and transparent.

9. The production method according to claim 7, wherein the addition rate of the sheet silicate to the solvent is 1 to 1.5 kg/min.

10. The method according to claim 7, wherein the temperature of the solvent is 18 to 25 ℃.