CN112029226A

CN112029226A - Polyformaldehyde composition and preparation method and application thereof

Info

Publication number: CN112029226A
Application number: CN202010879523.3A
Authority: CN
Inventors: 曹绍强; 黄险波; 叶南飚; 陈锋; 付学俊; 丁超
Original assignee: Kingfa Science and Technology Co Ltd
Current assignee: Kingfa Science and Technology Co Ltd
Priority date: 2020-08-27
Filing date: 2020-08-27
Publication date: 2020-12-04
Also published as: WO2022041591A1

Abstract

The invention discloses a polyformaldehyde composition and a preparation method and application thereof. The polyformaldehyde composition comprises the following components: polyformaldehyde, titanium dioxide, a lubricant, a main antioxidant, an auxiliary antioxidant and carbon black. According to the invention, a small amount of titanium dioxide and a trace amount of carbon black are added into polyformaldehyde and other components, and are matched with each other to prepare the polyformaldehyde composition. The polyformaldehyde composition has excellent shading performance, keeps a high L value, and avoids polyformaldehyde degradation foaming or finished product mechanical property reduction caused by adding a large amount of titanium dioxide. The preparation process of the polyformaldehyde composition is simple and convenient, is suitable for industrial large-scale production, and is beneficial to further popularization and application of the composition.

Description

Polyformaldehyde composition and preparation method and application thereof

Technical Field

The invention relates to the technical field of engineering plastics, and particularly relates to a polyformaldehyde composition as well as a preparation method and application thereof.

Background

Polyoxymethylene (POM) is a hard and dense material with a smooth, glossy surface, a pale yellow color, and a translucent thin-walled portion. The POM has excellent mechanical property, high strength and rigidity, good elasticity, good antifriction and wear resistance and good electrical insulation property, and is widely applied to the fields of electronics, electricity, machinery, instruments, daily light industry, automobiles, building materials, agriculture and the like.

Titanium dioxide and carbon black are usually added into POM to be used as a light shielding agent to reflect ultraviolet light and improve the weather resistance of the POM to the ultraviolet light. The addition amount of the titanium dioxide and the carbon black as the light shielding agent is generally 0.5-10 parts. Since the addition of titanium dioxide and carbon black can affect the color of POM, generally, carbon black is generally used as a light shielding agent when the color of the POM product is darker, and titanium dioxide is generally used as a light shielding agent when the color of the POM product is whiter. Chinese patent CN104371267A discloses a weather-resistant polyformaldehyde blend for automobiles, which is composed of polyformaldehyde resin, an ultraviolet absorbent, a light stabilizer, a light shielding agent and the like, wherein the addition amount of the light shielding agent is 0.5-5%, and the light shielding agent comprises titanium dioxide, carbon black and the like. The polyformaldehyde blend aims at improving the ultraviolet light resistance and the thermal oxidation aging resistance of polyformaldehyde resin, and does not relate to the shading performance of the polyformaldehyde blend and the color of the polyformaldehyde blend.

POM is not completely shaded, when the color of the POM is white and the thickness of the POM is less than 5mm, the thin-walled product prepared by the POM has partial light transmission, and the shading modification reports of the POM in the prior art are less. Due to market selection, product design and other reasons, product parts such as an internal key shaft of a computer keyboard are thin, about 2.0mm in thickness, need to be white, have the requirement of shading, and require the used materials to keep opaque under the condition of thin walls. Therefore, in order to apply POM to the aforementioned industries, it is necessary to modify the light-shielding property.

Therefore, development of a white POM having light-shielding properties in a thin wall is urgently required.

Disclosure of Invention

The invention provides a polyformaldehyde composition for overcoming the defect of poor light shielding performance of thin-wall POM in the prior art.

Another object of the present invention is to provide a process for producing the polyoxymethylene composition.

Still another object of the present invention is to provide the use of the above polyoxymethylene composition.

In order to solve the technical problems, the invention adopts the technical scheme that:

a polyoxymethylene composition comprises the following components in parts by weight:

85-98 parts of polyformaldehyde,

5-12 parts of titanium dioxide powder,

1.2 to 2.5 parts of a lubricant,

0.1-0.5 part of main antioxidant,

0.1-0.3 part of auxiliary antioxidant,

0.000008-0.00005 parts of carbon black.

The inventor finds that the light-shading performance of the POM can be greatly improved by adding titanium dioxide and a trace amount of carbon black into the POM composition and matching the titanium dioxide and the trace amount of carbon black, so that the POM composition achieves an excellent light-shading effect.

The inventor researches and discovers that when the adding amount of titanium dioxide in a POM system is large, the effect of shading can be achieved, but when the adding amount of titanium dioxide is large, POM can be degraded and foamed, and granulation cannot be produced. When carbon black is added into a POM system, the POM color is very easy to turn black. In the application, the addition of a very small amount of carbon black has no obvious influence on the white color of the POM composition, and the POM composition can keep a high white color L value; meanwhile, due to the reduction of the addition amount of the titanium dioxide, the degradation effect of the titanium dioxide on the POM is greatly reduced, so that the POM composition does not have the degradation foaming condition in the production process or the mechanical property of the finished POM composition is reduced.

Optionally, the titanium dioxide is anatase type titanium dioxide or rutile type titanium dioxide.

Preferably, the titanium dioxide is rutile type titanium dioxide.

The titanium dioxide has two crystal forms of rutile and anatase, namely rutile titanium dioxide, namely R type titanium dioxide; anatase titanium dioxide, i.e. type A titanium dioxide. Both titanium white powders have the characteristics of strong covering power, high tinting strength and the like. However, the rutile type titanium dioxide has more outstanding dispersibility and high whiteness, and the anatase type titanium dioxide has relatively poor stability and dispersibility, and can be converted into the rutile type titanium dioxide at high temperature.

The average particle size of the carbon black is 14-55 nm.

Preferably, the average particle size of the carbon black is 14 to 20 nm.

The average particle diameter of carbon black affects the coloring strength thereof. Generally, the lower the average particle size of the carbon black, the stronger its color strength. When the average particle size of the carbon black is too low, the carbon black is easy to agglomerate and difficult to disperse, and the dispersion effect is poor after the carbon black is mixed with other raw materials. The technical scheme of the application selects the carbon black with proper average particle size, and can achieve effective shading effect by using less additive amount.

Since polyoxymethylene is susceptible to acid decomposition, those skilled in the art generally use raw materials with a pH of 6.5 or more in the preparation of POM materials.

Preferably, the carbon black has a pH of 6.5 to 8.5.

Method for measuring the pH of carbon black the pH of the aqueous suspension is determined according to ISO 787-9 general test method for pigments and extender pigments, part 9: 5g of the sample was weighed and added to 50ml of deionized water, mixed well, left to stand, and then the pH value was measured using a pH meter.

Preferably, the melt index of the polyformaldehyde at 190 ℃ under the test condition of 2.16kg is 1-50 g/10 min; the density is 1.38 to 1.43g/cm³。

The lubricant may be a lubricant commonly used for polyoxymethylene.

Preferably, the lubricant is an amide-based lubricant and/or a polyethylene-based lubricant.

Preferably, the weight ratio of the amide lubricant to the polyethylene lubricant is (0.2-1.5): 1.

More preferably, the weight ratio of the amide-based lubricant to the polyethylene-based lubricant is 1.5: 1.

The amide lubricant has excellent high-temperature stability and interface lubrication; the polyethylene lubricant is used as an external lubricant, so that the adhesive force of the rubber material to a processing machine is greatly reduced.

The primary antioxidant may be a primary antioxidant commonly used for polyoxymethylene, for example a hindered phenolic antioxidant, preferably under the brand name basf IRGANOX 245.

The secondary antioxidant may be a secondary antioxidant commonly used for polyoxymethylene. Preferably, the auxiliary antioxidant is one or more of phosphite antioxidants and thioether antioxidants.

The invention also provides a preparation method of the polyformaldehyde composition, which comprises the following steps:

mixing polyformaldehyde, titanium dioxide, a lubricant, a main antioxidant, an auxiliary antioxidant and carbon black to obtain a premix, adding the premix into a double-screw extruder, and carrying out melt extrusion, cooling and granulation to obtain the polyformaldehyde composition.

Preferably, the temperatures of all the cylinders of the twin-screw extruder from the feeding port to the machine head are respectively as follows: 150 to 170 ℃, 160 to 180 ℃, 170 to 190 ℃, 180 to 200 ℃, a screw rotation speed of 250 to 400 revolutions per minute, a feeding amount of 50 to 200kg/h, and a vacuum degree of (-0.1) to 0 MPa.

Preferably, the mixing method of the premix in the preparation method comprises the following steps: weighing carbon black, adding the carbon black into the lubricant for pre-dispersion, and mixing the lubricant containing the carbon black with other raw materials to obtain the premix.

By adding and mixing carbon black by a pre-dispersion method, it is possible to uniformly mix the carbon black with other raw materials in a short time when the amount of the carbon black added is small.

The invention also protects the application of the polyformaldehyde composition in preparing thin-walled POM products.

In the invention, the thickness range of the thin wall is 1-3 mm.

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, a small amount of titanium dioxide and a trace amount of carbon black are added into polyformaldehyde and other components, and are matched with each other to prepare the polyformaldehyde composition. The polyformaldehyde composition has excellent shading performance, keeps a high white L value, and avoids the degradation foaming or the reduction of the mechanical performance of a finished product in the production process of POM (polyoxymethylene) caused by adding a large amount of titanium dioxide. The preparation process of the polyformaldehyde composition is simple and convenient, is suitable for industrial large-scale production, and is beneficial to further popularization and application of the composition.

Drawings

Fig. 1 is a diagram of grading standard of shading effect, wherein a is a shading effect grade 1, b is a shading effect grade 2, c is a shading effect grade 3, and d is a shading effect grade 4.

Detailed Description

The present invention will be further described with reference to the following embodiments.

The starting materials in the examples are all commercially available, and are specified below:

POM POM 25 Yunnan Tiantianhua GmbH, the melt index is 2.5g/10min (190 ℃/2.16KG), and the density is 1.4g/cm³；

POM M450 Yunnantian chemical Co., Ltd, the melt index was 45g/10min (190 ℃/2.16KG), and the density was 1.4g/cm³；

Titanium dioxide TR-33, rutile titanium dioxide, Jiangxi gloss chemical Co., Ltd;

VK-TA18, anatase titanium dioxide, Hangzhou Zhi Ti purification technologies, Inc.;

carbon black hilblack 49L, degussa black, average particle size 19nm, pH 8.0;

HIBLACK 970LB, Texaco carbon black, average particle size 14nm, pH 8.0;

HIBLACK 160B, Degussa carbon black, with an average particle size of 55nm and a pH of 8.5;

amide lubricants B50, N' -ethylene bis stearamide, indonesebar lubricant;

polyethylene lubricants 1105A, polymers of 2, 5-furandione with ethylene and 1-propylene, japan mitsui chemistry;

a primary antioxidant of basf IRGANOX 245, a hindered phenol antioxidant, bis [3- (1, 1-dimethylethyl) -4-hydroxy-5-methylpropanoic acid ] tripeleneglycol;

phosphite antioxidant SONOX 168, tris (2, 4-di-tert-butylphenyl) phosphite, Yuansheng chemical Co., Ltd, Fushan;

thioether antioxidant RIANOX 412S, pentaerythritol tetrakis (3-laurylthiopropionate), Tianjin Lianlong New materials GmbH.

Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Examples 1 to 13

Examples 1 to 13 provide polyoxymethylene compositions having the amounts of components shown in table 1.

TABLE 1 amounts (parts by weight) of each component added in examples 1 to 13

The specific addition amounts of the example 1 are as follows:

9.2kg of POM, 0.5kg of rutile titanium dioxide, 0.05kg of amide lubricant, 0.1kg of polyethylene lubricant, 0.03kg of hindered phenol antioxidant, 0.02kg of phosphite antioxidant and 49L of carbon black of 0.015 g.

The methods for preparing the polyoxymethylene compositions of examples 1 to 12 were all as follows:

mixing polyformaldehyde, titanium dioxide, a lubricant, a hindered phenol antioxidant, an auxiliary antioxidant and carbon black to obtain a premix, adding the premix into a double-screw extruder, and carrying out melt extrusion, cooling and granulation to obtain the polyformaldehyde composition.

Wherein, the temperature of each screw cylinder from the charging opening to the machine head of the double-screw extruder is respectively as follows: 150 to 170 ℃, 160 to 180 ℃, 170 to 190 ℃, 180 to 200 ℃, a screw rotation speed of 250 to 400 revolutions per minute, a feeding amount of 50 to 200kg/h, and a vacuum degree of (-0.1) to 0 MPa.

Example 13 a polyoxymethylene composition was prepared:

firstly, uniformly mixing carbon black and a lubricant, performing pre-dispersion on the carbon black, then mixing the mixed pre-dispersion, polyformaldehyde, titanium dioxide, hindered phenol antioxidant and auxiliary antioxidant to obtain a premix, adding the premix into a double-screw extruder, and performing melt extrusion, cooling and granulation to obtain the polyformaldehyde composition.

Comparative examples 1 to 7

Comparative examples 1 to 7 provide polyoxymethylene compositions having the amounts of components as shown in table 2.

TABLE 2 addition amounts (parts by weight) of respective components in comparative examples 1 to 7

The comparative examples 1 and 2 are different from the example 1 in that the addition amount of the titanium dioxide is different and is respectively 20 parts and 4.5 parts;

comparative examples 3 and 4 are different from example 1 in that the addition amounts of carbon black are 0.00007 parts and 0.000004 parts, respectively;

comparative example 5 differs from example 1 in that no titanium dioxide is added;

comparative example 6 differs from example 1 in that no carbon black was added;

comparative example 7 differs from example 1 in that no titanium dioxide and no carbon black are added.

The polyoxymethylene compositions of comparative examples 1 to 7 were prepared in the same manner as in examples 1 to 12.

Performance testing

The polyoxymethylene compositions prepared in the above examples and comparative examples were subjected to a performance test.

The test method specifically comprises the following steps:

shading effect: the polyoxymethylene compositions prepared in the above examples and comparative examples were respectively injection-molded into color plates of 2.0mm thickness by an injection molding machine, white light (wavelength 390 to 760nm) from an LED lamp was irradiated close to the color plates, and the light intensity was observed to determine whether the light was transmitted through the color plates or not and to determine the shading effect. The specific shading effect grading standard is shown in figure 1.

Shade level	Shading effect	Description of the invention
			Level 1	Superior food	The light can not penetrate the color plate, and the back of the color plate is completely dull
Stage 2	Sub-optimal	The light of the lamp passes through the color plate at least partially, and the back of the color plate has slight light
			Grade 3	Medium and high grade	The light part penetrates the color plate, and the back of the color plate has obvious light
4 stage	Difference (D)	The light totally penetrates the color plate, and the back of the color plate has strong light

L value: CIE 15:2004 colorimetric, detection equipment: x. rite Color-Eye 7000A;

extrusion pelletizability: observing the particle condition in the preparation process, wherein the surface of normal particles is intact, 1-2 vacuum holes are arranged in the middle, and no crushing is performed; the foamed particles are in the form of expanded or crushed particles;

tensile strength: ISO527-2 test for tensile Properties of plastics;

notched impact strength: ISO180 Plastic notched impact strength test.

The test results of examples 1 to 13 are shown in Table 3.

Table 3 results of testing the Performance of examples 1 to 13

As can be seen from Table 3, the light-shielding effects of the polyoxymethylene compositions prepared in examples 1 to 13 are all 1-grade or 2-grade, and the polyoxymethylene compositions can effectively shield light under the irradiation of LED light. Meanwhile, the L value of each polyformaldehyde composition reaches more than 85, which shows that the polyformaldehyde composition is white in appearance and does not have obvious graying and blackening conditions. In the preparation process of the above embodiment, each polyoxymethylene composition is normally extruded and pelletized, and no foaming occurs, which indicates that the addition of titanium dioxide and carbon black according to the technical scheme of the present application does not degrade POM and thus affects the preparation of polyoxymethylene compositions.

As can be seen from the tensile strength and notched impact strength in Table 3, the practiceThe polyformaldehyde compositions prepared in examples 1-13 have good mechanical properties, and the tensile strength is not less than 55MPa, and the notch impact strength is not less than 7.8KJ/m²。

The test results of comparative examples 1 to 7 are shown in Table 4.

TABLE 4 comparative examples 1-7 Performance test results

As can be seen from Table 4, the POM is degraded to a certain extent due to excessive addition of titanium dioxide, so that the polyformaldehyde composition prepared in comparative example 1 has foaming phenomenon during extrusion granulation, is poor in tensile strength and notch impact strength, and affects shading effect, and the shading effect is grade 3. The titanium dioxide of comparative example 2 is too little in addition and poor in shading effect; and because the addition amount of the titanium dioxide is too small and the carbon black is added at the same time, the L value of the polyformaldehyde composition is lower and cannot meet the white requirement. The polyformaldehyde composition of comparative example 3 has good shading effect and good mechanical property, but because the addition amount of the carbon black is large, the L value is only 78 and is far lower than 85 which can meet the requirement, and the whole color of the polyformaldehyde becomes dark. The carbon black of comparative example 4 was added in an excessively small amount, and the polyoxymethylene composition was poor in light-shielding effect. Comparative example 5 No titanium dioxide was added, the polyoxymethylene composition was darker in color, the L value was 66, and the light-shielding effect was only grade 3. Comparative example 6 No carbon black was added, and the light-screening effect of the polyoxymethylene composition was class 4, and the light-screening requirement was not met. Comparative example 7 has no titanium dioxide and carbon black added, which results in the polyoxymethylene composition having poor light-shielding effect and deep color.

Comparing the mechanical properties, i.e., tensile strength and notched impact strength, of the polyoxymethylene compositions of examples 1 to 13 and comparative example 7, it can be seen that the mechanical properties of the remaining examples are equivalent to those of comparative example 5 except that the mechanical properties of example 6 are slightly lower. In general, the notched impact strength of the polyoxymethylene compositions is required to be 7.5kJ/m or more²This indicates that the mechanical properties of example 6 are also within an acceptable range. While the notched impact strength of the polyoxymethylene composition of example 11 was required to be 9.2KJ/m²This shows that the polyoxymethylene composition has better mechanical properties when the weight ratio of the amide-based lubricant to the polyethylene-based lubricant is 1.5: 1.

In conclusion, the polyformaldehyde composition prepared according to the technical scheme of the application maintains white color, improves the light shading performance of the polyformaldehyde composition, and simultaneously has no obvious reduction of the mechanical performance compared with the polyformaldehyde composition without adding titanium dioxide and carbon black.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. The polyformaldehyde composition is characterized by comprising the following components in parts by weight:

85-98 parts of polyformaldehyde, 5-12 parts of titanium dioxide, 1.2-2.5 parts of lubricant, 0.1-0.5 part of main antioxidant, 0.1-0.3 part of auxiliary antioxidant and 0.000008-0.00005 part of carbon black.

2. The polyoxymethylene composition of claim 1, wherein the titanium dioxide is rutile titanium dioxide or anatase titanium dioxide.

3. The polyoxymethylene composition of claim 1, wherein the carbon black has an average particle diameter of 14 to 55 nm.

4. The polyoxymethylene composition of claim 1, wherein the carbon black has an average particle diameter of 14 to 20 nm.

5. The polyoxymethylene composition of claim 1, wherein the carbon black has a pH of 6.5 to 8.5.

6. The polyoxymethylene composition of claim 1, wherein the polyoxymethylene has a melt index of 1 to 50g/10min at 190 ℃ under a load of 2.16 kg.

7. The polyoxymethylene composition of claim 1, wherein the lubricant is a mixture of an amide-based lubricant and/or a polyethylene-based lubricant.

8. A process for producing the polyoxymethylene composition of claim 1 to 7, comprising the steps of:

mixing polyformaldehyde, titanium dioxide, a lubricant, a main antioxidant, an auxiliary antioxidant and carbon black, adding the mixture into a double-screw extruder, and performing melt extrusion, cooling and granulation to obtain the polyformaldehyde composition.

9. Use of the polyoxymethylene composition of claim 1 to 7 in the production of a thin-walled polyoxymethylene article.

10. The use according to claim 9, wherein said thin wall has a thickness in the range of 1 to 3 mm.