阅读说明：本技术 一种用于绝热管道低点水平浇注聚氨酯的生产工艺 (Production process for low-point horizontal casting polyurethane for heat-insulating pipeline ) 是由 刘建立 王忠生 郝友利 李景军 于海林 孙连鹏 于 2020-10-26 设计创作，主要内容包括：本发明提供了一种用于绝热管道低点水平浇注聚氨酯的生产工艺,包括以下步骤：清理发泡机的枪头针阀和发泡机预混合箱的黑料滤网、白料滤网；向黑料罐内注入黑料,向白料罐内注入白料；待填充内胆的外围通过外壳支撑模具套接至待填充外壳的内圈；通过温控控制柜将相关装置进行预热；通过发泡机的预混合箱将黑料和白料按照特定比例进行预混合；通过发泡机的注射枪头把黑料和白料的混合物注入外壳和内胆之间的所述缝隙内；进行保压熟化；通过温控控制柜将发泡机和外壳支撑模具进行进行冷却。本发明所述的一种用于绝热管道低点水平浇注聚氨酯的生产工艺,解决了发泡料在夏季温度过高时,发泡料容易反应时间短,起发快,而造成的发泡密度不均匀。(The invention provides a production process for low-point horizontally-poured polyurethane for a heat-insulating pipeline, which comprises the following steps of: cleaning a gun head needle valve of a foaming machine and a black material filter screen and a white material filter screen of a pre-mixing box of the foaming machine; injecting black materials into the black material tank, and injecting white materials into the white material tank; the periphery of the inner container to be filled is sleeved to the inner ring of the shell to be filled through the shell supporting die; preheating the relevant device through a temperature control cabinet; premixing the black material and the white material according to a specific ratio through a premixing box of a foaming machine; injecting the mixture of the black material and the white material into the gap between the shell and the inner container through an injection gun head of a foaming machine; performing pressure maintaining and curing; and cooling the foaming machine and the shell supporting die through the temperature control cabinet. The production process for the low-point horizontal casting polyurethane for the heat-insulating pipeline solves the problems that when the temperature of a foaming material is too high in summer, the foaming material is easy to react for a short time and quickly rises, and the foaming density is not uniform.)

1. A production process for low-point horizontal casting polyurethane of a heat insulation pipeline is characterized by comprising the following steps: comprises the following steps;

s1, cleaning a gun head needle valve of the foaming machine and a black material filter screen and a white material filter screen of a pre-mixing box of the foaming machine;

s2, injecting black materials into the black material tank, and injecting white materials into the white material tank;

s3, sleeving the periphery of the inner container to be filled to the inner ring of the shell to be filled through a shell supporting die, and arranging a gap between the shell to be filled and the inner container to be filled;

s4, preheating black materials, white materials, a foaming machine, a shell to be filled, an inner container to be filled and a shell supporting die through a temperature control cabinet;

s5, premixing the black material and the white material according to a specific ratio through a premixing box of a foaming machine;

s6, injecting the mixture of the black material and the white material into the gap between the shell and the inner container through an injection gun head of a foaming machine;

s7, performing pressure maintaining and curing;

and S8, cooling the foaming machine and the shell supporting die through the temperature control cabinet.

2. The process according to claim 1 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: the black material is made of polyisocyanate; the white material is a mixture of polyether, a foaming agent, a catalyst and a foam stabilizer.

3. The process according to claim 2 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: the foaming agent is made of purified water.

4. The process according to claim 1 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: in the step 4, the working temperature ranges of the black material and the white material are 18-25 ℃, the working temperature range of the shell supporting die is 40 +/-5 ℃, the working temperature range of the foaming machine is 35-55 ℃, and the working temperature ranges of the shell to be filled and the inner container to be filled are 35-50 ℃.

5. The process according to claim 1 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: the proportion of the black material to the white material in the step 5 is 145: 100.

6. the process according to claim 1 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: in the step 5, the stirring time of a premixing box of the foaming machine is 6s, the milk-white time of the black material and white material mixture is 14-18s, the gel time of the black material and white material mixture is 70-86s, and the non-sticking time of the black material and white material mixture is 125-155 s.

7. The process according to claim 1 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: and 7, controlling the injection pressure of the mixture of the black material and the white material injected by an injection gun head of the foaming machine in the step 7 to be 13-16 MPa.

8. The process according to claim 1 for the production of low-point horizontally poured polyurethane for insulated pipes, characterized in that: and in the step 7, the curing time of the mixture of the black material and the white material is 5-20 min.

Technical Field

The invention belongs to the technical field of heat-insulating pipeline construction, and particularly relates to a production process for low-point horizontal pouring of polyurethane for a heat-insulating pipeline.

Background

With the increasingly reduced and growing demand of world energy sources, energy conservation, emission reduction and environmental protection become global development trends, and the governments of the country and various regions also advocate the development, application and industrialization of energy conservation, emission reduction and environmental protection products. In recent years, with the rapid development of the building energy-saving market in China, polyurethane rigid foam heat-insulating products are widely applied to the field of building heat-insulating and waterproof, and become one of the heat-insulating and energy-saving products in the leading market.

Simultaneously with the centralization of urban heating and the enlargement of the heat supply face, the main pipe network of urban heat supply pipelines will be bigger and bigger, and simultaneously because the haze pollution phenomenon is serious day by day in recent years, heat supply companies in large cities will continuously move out of the cities or stop supplying heat, adopt the waste heat of power plants to supply heat, change to the cogeneration of heat and electricity. As the heat supply distance is increased, the caliber of a heat supply pipeline is further increased, and the application of the large-caliber polyurethane direct-buried heat insulation pipeline becomes a necessary trend in China.

The polyurethane direct-buried heat-insulating pipe is also called pipe-in-pipe, and is formed by two steps, and is composed of a high-density polyethylene outer protective layer, a polyurethane rigid foam plastic pipe and a steel pipe. The material of the heat-insulating layer has the density of 60kg/m³To 80kg/m³The rigid polyurethane foam fully fills the gap between the steel pipe and the sleeve pipe, and has certain bonding strength, so that the steel pipe, the outer sleeve pipe and the heat-insulating layer form a firm whole. The polyurethane directly-buried insulating pipe foam has good mechanical property and thermal insulation property, and the polyurethane foamed insulating pipe is widely used for liquid and gas conveying pipe networks, chemical pipeline insulating engineering petroleum, chemical engineering, central heating networks, central air-conditioning ventilation pipelines, municipal engineering and the like.

The high-temperature prefabricated direct-buried heat-insulating pipe is a direct-buried prefabricated heat-insulating pipe which has good heat-insulating property, safety, reliability and low engineering cost. The problems of heat preservation, sliding lubrication and water prevention of pipe ends of prefabricated direct-buried heat preservation pipes for high-temperature heat transmission at 130-180 ℃ in urban centralized heat supply are effectively solved. The high-temperature prefabricated direct-buried heat-insulating pipe adopts a direct-buried heat-supplying pipeline technology, and marks that the technical development of the Chinese heat-supplying pipeline has entered a new starting point.

However, the last production process of the high-temperature prefabricated direct-buried heat-insulation pipe is foaming heat insulation, so that the conditions of uneven density at two ends of the pipeline, bubbles, bulges and the like frequently occur after injection, the quality of the product of a company is unstable, and the situation of bulging or unqualified density of the heat-insulation layer is frequently subjected to random inspection after production and during the period of pipeline backfilling on site.

Disclosure of Invention

In view of the above, the present invention is directed to a production process for low-point horizontal casting of polyurethane for heat-insulating pipes, so as to solve the deficiencies of the prior art.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a production process for low-point horizontal casting polyurethane of an insulated pipeline comprises the following steps: s1, cleaning a gun head needle valve of a foaming machine and a black material filter screen and a white material filter screen of a foaming machine pre-mixing box, wherein the model of the foaming machine is PU 600; s2, injecting black materials into the black material tank, and injecting white materials into the white material tank; s3, sleeving the periphery of the inner container to be filled to the inner ring of the shell to be filled through a shell supporting die, and arranging a gap between the shell to be filled and the inner container to be filled; s4, preheating black materials, white materials, a foaming machine, a shell to be filled, an inner container to be filled and a shell supporting die through a temperature control cabinet; s5, premixing the black material and the white material according to a specific ratio through a premixing box of a foaming machine; s6, injecting the mixture of the black material and the white material into the gap between the shell and the inner container through an injection gun head of a foaming machine; s7, performing pressure maintaining and curing; and S8, cooling the foaming machine and the shell supporting die through the temperature control cabinet.

Further, the black material is made of polyisocyanate; the white material is a mixture of polyether, a foaming agent, a catalyst and a foam stabilizer.

Further, the foaming agent is made of pure water.

Further, in the step 4, the working temperature ranges of the black material and the white material are 18-25 ℃, the working temperature range of the shell supporting die is 40 +/-5 ℃, the working temperature range of the foaming machine is 35-55 ℃, and the working temperature ranges of the shell to be filled and the inner container to be filled are 35-50 ℃.

Further, the proportion of the black material to the white material in the step 5 is 145: 100.

further, the stirring time of a premixing box of the foaming machine in the step 5 is 6s, the cream time of the black material and white material mixture is 14-18s, the gel time of the black material and white material mixture is 70-86s, and the non-sticking time of the black material and white material mixture is 125-155 s.

Further, the injection pressure of the mixture of the black material and the white material injected by the injection gun head of the foaming machine in the step 7 is controlled to be 13-16 MPa.

Further, in the step 7, the aging time of the mixture of the black material and the white material is 5-20 min.

Compared with the prior art, the production process for the low-point horizontal casting polyurethane of the heat-insulating pipeline has the following advantages:

(1) according to the production process for the low-point horizontal casting polyurethane of the heat-insulating pipeline, disclosed by the invention, through the preheating of related devices and the proportioning of raw materials, the efficiency and the quality of polyurethane production reaction are ensured, the uniform density of the polyurethane filled in the pipeline is ensured, the product quality is high, the yield is high, and the process is simple and convenient.

(2) The production process for the low-point horizontal casting polyurethane for the heat-insulating pipeline solves the problems that when the temperature of a foaming material is too high in summer, the foaming material is easy to react for a short time and quickly rises, and the foaming density is not uniform.

Detailed Description

It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

The terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The present invention will be described in detail with reference to examples.

A production process for low-point horizontal casting polyurethane of a heat insulation pipeline comprises the following steps;

s1, cleaning a gun head needle valve of the foaming machine and a black material filter screen and a white material filter screen of a pre-mixing box of the foaming machine; s2, injecting black materials into the black material tank, and injecting white materials into the white material tank; s3, sleeving the periphery of the inner container to be filled to the inner ring of the shell to be filled through a shell supporting die, and arranging a gap between the shell to be filled and the inner container to be filled; s4, preheating black materials, white materials, a foaming machine, a shell to be filled, an inner container to be filled and a shell supporting mold through a temperature control cabinet; s5, premixing the black material and the white material according to a specific ratio through a premixing box of a foaming machine; s6, injecting the mixture of the black material and the white material into the gap between the shell and the inner container through an injection gun head of a foaming machine; s7, performing pressure maintaining and curing; and S8, cooling the foaming machine and the shell supporting die through the temperature control cabinet.

The black material is polyisocyanate, which is a black viscous liquid, so the black material is commonly called black material. The main varieties of the polyisocyanates are MDI, TDI and PAPI, the black materials are easy to chemically react with water, the container is guaranteed to be dry and sealed and filled with dry nitrogen for protection in the storage process, and the black materials are not directly contacted with the water in the using process. Crystallization occurs at storage temperatures below 5 ℃ and care must be taken to prevent freezing. Once the crystal appears, the crystal is heated and melted at 70-80 ℃ before use, and is fully and uniformly stirred. Storage temperatures above 50 ℃ produce an insoluble solid, increase in viscosity, and change in chemical properties. The same properties are present for the white material. The black material and the white material are required to be stored in a ventilated, shady and dry place at room temperature (20-25 ℃) to avoid sunshine and rain, the black material and the white material are subjected to constant temperature treatment before foaming, the foaming temperature is controlled to be 18-25 ℃ through a temperature control cabinet, and when the temperature is too low, the black material and the white material have high viscosity, unstable flow, poor fluidity and uneven mixing. When the temperature is too high, the reaction is violent and difficult to control, the performance of injected foam liquid is not uniform, the foam liquid which is injected at the beginning is subjected to chemical reaction, the viscosity is rapidly increased, and the foam liquid which is injected later is not reacted.

The white material is a mixture of polyether, a foaming agent, a catalyst and a foam stabilizer, the mixture is a white viscous liquid commonly known as white material, wherein the catalyst mainly plays a role in accelerating the formation of polyurethane, shortening the curing time and improving the foaming quality, the foam stabilizer mainly plays a role in emulsifying each raw material component in a system, the smooth proceeding of the system reaction is ensured, the nucleation of bubbles is promoted, the stability of bubble walls is improved, the product has uniform and fine foam pores and good mechanical properties, the dosage of the foam stabilizer is small, but the foam stabilizer has a great influence on the foam structure, physical properties and manufacturing process, in the polyurethane foaming, the foaming agent mainly plays a role in generating gas, fine and uniformly distributed bubbles are formed in the polyurethane, and the foaming agent does not participate in the chemical reaction between polyisocyanate and combined polyether, the foaming process using freon (e.g., R11, R12) as a foaming agent is called freon foaming, the foaming process using a foaming agent containing no freon is called freon-free foaming such as cyclopentane foaming, and the material of the foaming agent in this example is purified water.

The working temperature range of the shell supporting die is 40 +/-5 ℃, and when the temperature of the shell supporting die is too low, the fluidity of a bubble liquid system is poor, the curing time is long, the reaction is incomplete, and vacuoles appear; when the temperature of the shell supporting mold is too high, the plastic inner container is deformed by heating, the reaction of a foaming liquid system is severe, the working temperature range of the foaming machine is 35-55 ℃, the working temperature ranges of the shell to be filled and the inner container to be filled are both 35-50 ℃, the temperature of the shell supporting mold and the environmental temperature of the foaming machine must be strictly controlled, particularly, in winter, the shell supporting mold, the foaming machine, the shell to be filled and the inner container to be filled must be preheated for more than 30 minutes, and after foaming in summer for a period of time, the foaming machine must be cooled.

The proportion of the black material to the white material in the step 5 is 145: 100, under the condition that the total injection amount is not changed, the blank material proportion is too large, the soft foam is generated, the foaming agent proportion is too large, the expanding foam is generated, and the foaming agent proportion is too small, the cavity is generated. The ratio of the black material to the white material is not adjusted, the material mixing is not uniform, the foam shrinks, and the injection amount of the mixture of the black material and the white material is based on the actual requirement. When the injection amount of the mixture of the black material and the white material is lower than the process requirement amount, the foam molding density is low, the strength is low, and even the phenomenon of filling non-compact cavities occurs. When the injection amount is higher than the process requirement, the phenomena of bubble expansion and bubble leakage can occur, and the inner container to be filled and the shell to be filled deform.

The premixing box of the foaming machine comprises 4 helical blades and a guide ring with the length of 6 cm, the materials are stirred at the speed of 2000 rpm and the stirring time is 6s, black materials and white materials are mixed through an injection gun head of a high-pressure foaming machine and injected into an interlayer between a shell and an inner container of a box body or a door body, under the condition of certain temperature, polyisocyanate (-NCO) and conjugate polyether (hydroxyl (-OH)) are subjected to chemical reaction under the action of a catalyst to generate polyurethane, and simultaneously a large amount of heat is released, at the moment, a foaming agent premixed in the conjugate polyether is continuously vaporized to ensure that the polyurethane expands to fill a gap between the shell and the inner container, and the chemical reaction formula is nO-N-R-N-C-O + N-R '-OH- (OC-NH-R-NH-COO-R' -O-) N, of polyurethanesThe milk-white time is 14-18s, the gel time of the polyurethane is 70-86s, the non-stick time of the polyurethane is 125-155s, and the performance requirements of the polyurethane foam are as follows: 1. free foaming density: 24 to 27Kg/m³(ii) a 2. Polyurethane molded density: 34-36 Kg/m³(ii) a 3. Compressive strength: not less than 0.20 MPa; 4. coefficient of thermal conductivity: less than or equal to 19.6 mw/m.k; 5. dimensional stability (-30 ℃, 24 h): less than or equal to 1.0 percent; 6. the closed pore rate is more than or equal to 97 percent.

And 7, controlling the injection pressure of the mixture of the black material and the white material injected by an injection gun head of the foaming machine in the step 7 to be 13-16MPa, and when the injection pressure is unstable, the proportion of the black material and the white material is unstable and the mixture is not fully mixed. The difference between the injection pressures of the black material and the white material is controlled within 5MPa, otherwise, the phenomenon that the foaming machine is damaged by material mixing can occur. The injection pressure of the foaming machine should be checked frequently in the foaming process, the injection system of the foaming machine is cleaned, and the phenomenon of material blockage cannot occur. The black, white and cyclopentane are mixed unevenly and are expressed in that the density of polyurethane foam is uneven, large bubbles appear locally, the foam cracks and the foam is soft locally: white, yellow or black streaks appear on the foam and the foam collapses.

In the step 7, the curing time of the mixture of the black material and the white material is 5-20min, the curing time is too short, the shell still foams after supporting the mould, and the problems of appearance deformation, large gap, cold leakage, heat insulation failure of the box body, frequent starting of a compressor and the like occur.

The chemical properties of polyisocyanate, combined polyether, foaming agent, catalyst and foam stabilizer in the black material and white material directly determine the chemical reaction and foam physical properties of the synthesized polyurethane, and are the basic conditions for producing qualified polyurethane foam. The black material and white material monomers are clear viscous liquid without flocculent insoluble impurities, if the black material and the white material monomers have the insoluble impurities, a filter screen of a foaming machine is blocked, so that the flow of raw materials is unstable, the mixture ratio of the black material and the white material is not in accordance with the requirement, the mixture is not uniform, even the pipeline of the foaming machine is blocked and the blanking is not carried out, and a gun head needle valve of the foaming machine and the black material filter screen and the white material filter screen of a pre-mixing box of the foaming machine are cleaned before each production and processing.

In the heat-insulating foaming process of the existing heat-supply pipeline, density unevenness and cavities inevitably occur, and particularly, in summer, swelling often occurs, the invention effectively solves the problems of non-uniform heat-insulating layer and unsatisfactory heat-insulating effect of the heat-insulating pipeline, and can effectively avoid the problem of equipment swelling under the condition of high temperature in summer.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.