Production process of engineered quartz stone slabs

Keywords: artificial quartz stone; engineered quartz stone; application; raw materials; production technology

1 Introduction

Engineered stone made of natural quartz stone (sand, powder), silica sand, tailings slag, and other inorganic materials (the main component of which is silica) and a certain amount of binding material, referred to as quartz stone or artificial quartz stone. It is a kind of composite building material that is vibrated and pressed under vacuum conditions, the plate structure is dense and non-porous, the surface is uniform, the hardness and other performance indicators are superior to natural granite and marble. Artificial quartz stone has become an emerging countertop material in the world. With its natural texture, super high hardness, and super wear resistance, it has gradually become one of the green and environmentally friendly building materials decorative products loved by the majority of consumers. In Europe and the United States, more and more consumers enter the family. Especially at the International Cabinet Show in Milan in 2006, this trend can be clearly felt in new products launched by famous cabinets from all over the world, especially the cabinet board industry has begun to be fully used, and the demand has increased greatly, providing production and development of quartz stone plates. A lot of space.

2 Characteristics and application fields of Engineered quartz stone

The quality of the quartz stone is gorgeous, the color is gorgeous and there is no lack of simplicity. Because its decorative effect is different from natural stone and ceramic tiles, it is favored by public engineering and home decoration designers abroad. Quartz stone is the Jiaozi in the countertop material, and it is also a rookie in the wall and floor decoration materials. The upsurge of quartz stone decoration has arrived.

Compared with natural stone, the characteristics of artificial quartz stone have the following advantages.

(1) Toughness is better than natural stone;

(2) The porosity is lower than that of natural stone, and the plate is resistant to contamination;

(3) No radiation;

(4) The strength is more than double that of natural marble, and the strength of pure quartz slab is even higher than that of granite;

(5) The raw materials of artificial quartz stone are selected and pre-mixed, which can be paved on a large area without color difference, which is suitable for large-scale engineering use.

Compared with ceramics, artificial quartz stone has the following advantages.

(1) Compared with ceramics, artificial quartz stone slabs have large specifications. The maximum size is currently 1.6 m × 3.2 m, and the thickness is 8-40 mm, which is suitable for processing and decoration on various occasions;

(2) Artificial quartz stone slabs are formed under vacuum, high pressure and high vibration, with low water absorption rate and stronger stain resistance than ceramics;

(3) The Engineered quartz stone slab has better toughness than ceramics and is easier to process. The surface hardness is close to that of polished tiles;

(4) Engineered quartz stone is green and environmentally friendly, without radiation;

(5) The artificial quartz stone has a good decorative effect and rich colors, which is inferior to any ceramic wall and floor tiles;

(6) The surface effect of the artificial quartz stone plate is soft and shiny, suitable for use in various high-end places;

(7) Raw materials with special effects can be added to the raw materials of artificial quartz stone, which can achieve the simple or luxurious effect required by customers.

Quartz stone has a special decorative effect. Its texture is natural, noble, bright, and comfortable, with no deformation, no fading, no radiation, no micropores, high density, high hardness, anti-aging, and so on. So its application field has expanded from home improvement to large-scale engineering. Artificial quartz slate has a wide range of fields, such as:

1) Walls, floors, elevator door covers, bathroom countertops, etc. in large shopping malls;

2) Walls, floors, toilets, exterior walls, etc. of high-end office buildings (Beijing Olympic Village, International Trade Building, etc.);

3) Hospital interior walls, exterior walls, floors, bathroom floors, washbasin countertops, etc .;

4) Walls, floors, exterior walls, etc. of stations, subway stations, airports, etc. (eg: Shenzhen Subway Station, Hong Kong Airport, Mumbai Airport, India, airports in many European countries, etc.)

5) Wall and floor laying, kitchen countertops, etc. for high-end residential home improvement;

6) Walls and floors of star hotels, bar countertops, etc.

3 The production process of engineered quartz stone

The production process of artificial quartz stone is shown in Figure 1.

(1) Selection of production materials

The quality of raw materials directly affects the quality of quartz stone, so it is very important to choose the raw materials from the source.

Selection of quartz powder: 1) Fineness requirement: 325 mesh or 400 mesh; 2) Whiteness requirement: 95 or above; 3) SiO2 content: above 98%.

Selection of quartz sand: Generally, as long as the hardness is sufficient, any color, appearance, and particle size can be used (the particle size does not exceed 1/2 of the thickness of the plate). High-purity quartz can produce pure color plates, such as pure blackboard, pure whiteboard, etc. Ordinary quartz sand: fewer white weathered particles, a few black and brown particles as possible. Selected quartz sand: spread the sand on a flat surface, black or other colored particles ≤1 (this requirement can be achieved by manual selection).

Resin: unsaturated polyester resin, polymer solid content: about 65%, appearance: colorless, light green, light yellow and transparent, preferable resin for artificial stone, this type of resin shrinks little, and the flatness of the board is good, Will not be deformed or cracked; In addition, try to choose a resin with low viscosity, the amount of this resin is relatively low.

Color: In the selection process of artificial quartz stone raw materials, in order to ensure the weather resistance of the material, try to use inorganic color. However, organic materials such as carbon black and red with stable weather resistance can also be used. The commonly used colors in the production of quartz stone include R902 white, 4920 yellow, phthalocyanine green, phthalocyanine blue, permanent solid purple, scarlet powder, permanent solid red, 4330 black, carbon black, BK03 special black, etc. In the production of artificial quartz stone, there are two ways to add colorants: one is to add resin to prepare a color paste and then use it; the other is to directly add it to the sand powder material and use it after mixing. The latter kind of addition method should ensure the uniformity of the pigment, and the equipment requirements are relatively high.

Figure 1 Production process of artificial quartz stone

Curing agent: an indispensable auxiliary agent for the production of quartz stone. Generally, artificial quartz stone is formed by high-temperature curing. The curing agent is a substance or mixture that promotes or controls the curing reaction of the resin. Resin curing is through condensation, ring closure, addition or catalysis, and other chemical reactions so that the thermosetting resin undergoes an irreversible change process. Curing is accomplished by adding curing (crosslinking) agent. Generally, diethylhexanoic acid tert-butyl ester curing agent is used, and the curing agent generally uses 0.8% to 1.2% of the resin content.

Coupling agent: It can improve the dispersion and adhesion of the filler in the resin, improve the process performance, and improve the mechanical, electrical, and weather resistance properties. The commonly used silane coupling agent is KH-570, and KH560 is recommended for plates with high-quality requirements.

(2) Color paste coloring

The mixing time of the color paste, the ratio of resin and color material will directly affect the color of the plate.

(3) Mixing and stirring

In the production process of artificial quartz stone plates, a single raw material is pre-mixed according to the production order or batch before use to reduce color difference; when stirring, a planetary high-speed mixer is used to ensure that the raw materials are fully mixed.

(4) Fabric

Carry out the cloth in the cloth device to meet the production requirements.

(5) Press suppression

The artificial quartz stone plate is formed under the action of high pressure and strong vibration force under vacuum, and the produced artificial quartz stone plate has high density and low water absorption rate. The pressurization time varies according to the formula and the thickness of the board, generally 2 to 4 minutes. After the artificial quartz stone board is pressed, the paper must be uncovered to ensure that the adhesion of each part to the paper/film is consistent, and no partial When the drum is touched by fingers, the entire board surface must be of the same softness.

(6) Curing

The pressed quartz stone plate is then sent into the furnace for thermal curing, in which the setting of the curing line of the curing furnace is particularly important because the temperature of the curing line is directly related to the deformation of the cured quartz stone plate: if the temperature of the curing line is too low, it will lead to the later deformation Large; if the temperature on the curing line is not uniform, it will cause stress on the surface and local parts of the plate. During the later polishing process, the plate will be deformed due to stress release. After the quartz slab comes out of the curing line, use iron pipes with a wall thickness of less than 3 mm to lightly tap various parts of the plate. If the sound is crisp, it means that the curing effect is good; if the sound is dull, it means that the curing effect is not good.

(7) Placement of semi-finished products after curing

For the placement of the semi-finished board, if the shrinkage of the resin is small, the bottom of the board can be placed on the A-frame vertically; if the shrinkage of the resin is large, it is recommended to lay the board flat to the bottom, and the surface of the board must be cleaned, ensure the flatness of the plate later. After solidification, the board must be placed for 24 h, and the polishing process can not be performed until the board is completely cooled.

(8) Polishing

The smaller the particle size, the lower the gloss. The gloss after polishing is generally around 40 °. The larger the particle size, especially the plate containing large-particle glass, the higher the gloss. The gloss after polishing is generally around 60 °. Selection of polished surface: the surface in contact with the template is generally used as the polished surface because the flatness and smoothness of this surface are better. This surface has fewer impurities in the fabric process, and this surface has high density during curing. Therefore, it is ideal to choose this side as the polished surface. Selection of grinding block: choose good quality granite stone grinding block and reasonable mesh matching. Polishing speed: The polishing speed varies depending on the raw material formula and the color of the plate. For example, for small particles and pure color plates, the linear speed should be slowed down during the polishing process; while for large particles and glass particles and light-colored plates, the linear speed can be relatively faster.

4 Common problems and solutions in the production process of artificial quartz stone plate

In the production process of quartz stone, due to improper operation control, various defects such as deformation, cracking, discoloration, discoloration, dusting, watermarks, pinholes, pores, impurities, etc. will occur. How to avoid these defects and reduce the waste of cost, sum up the following experience:

Deformation: It is mainly related to the composition of the formula, the curing method, whether the curing is sufficient, and whether the storage method of the semi-finished product / finished product is appropriate. The solutions are as follows: 1) Formulate a reasonable formula structure, adopt reasonable curing methods and accurate curing methods such as secondary curing technology, and heat the board up and down during the movement to be fully heated. 2) Choose a reasonable storage method according to the quality of the resin.

Discoloration: Discoloration is mainly related to the properties of the resin, colorants, and curing agents. The solution is as follows: 1) Use a resin with good stability. 2) A thermal curing agent is used to ensure that the curing agent can fully react without residue during the heating process. 3) Adopt inorganic pigments, good weather resistance.

Pores: Pores are divided into two categories, one is small pinholes, usually because the vacuum can not reach -0.1MPa, and the resin content in the formula is too high; the second is large irregular pores, usually because of the formula structure Unreasonable, uneven cloth, not compact when pressed by the press, and uneven cloth force. The method of prevention is: First, use good vacuum equipment, use special vacuum pump oil and do good maintenance; Second, the seal of the press and the pipeline is better, and the vacuum chamber of the press is smaller; Third, it must be formulated The formula structure; Fourth, we must have good molding equipment and mature production technology and operating procedures. Watermark: The appearance of the watermark is caused by uneven pressure and uneven movement of the plate during the pressing process, which results in uneven distribution of the toner used inside the plate. However, under the control of a mature production process, a press with strong pressure and vibration can prevent this problem.

Wear scars: Wear scars are the most common problem, especially on dark and solid boards. The use of special grinding blocks can reduce or eliminate such dark marks, and choose a reasonable polishing speed according to the color of the plate and the particles.

5 Conclusion

There is no doubt about the market space of quartz stone, and artificial quartz stone slabs have replaced some natural stones and ceramic products as a development trend. At present, there are still some quality problems or product defects, and the production technology needs to be further improved, but the artificial quartz plate has excellent physical properties and decorativeness. In recent years, it has gained rapid popularity in economically developed countries. In addition, due to the environmental protection of artificial quartz stone, in today’s emphasis on low-carbon environmental protection, many space designers prefer artificial stone to natural stone. Therefore, the consumption habits of quartz plates will inevitably expand to the whole world.