Hot melt adhesive with high adhesive property and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, in particular to a high-adhesive-property hot melt adhesive and a preparation method thereof.The preparation method comprises the steps that an ethylene-vinyl acetate copolymer is prepared, the molten state of the copolymer is judged according to the melt flow rate, and the copolymer serves as a base material to be added into a reaction kettle; adding auxiliary materials mixed in proportion into the reaction kettle, and mixing and stirring the base material and the auxiliary materials; detecting the dispersity of the auxiliary material in the base material, and adjusting the rotating speed of the screw rod according to the dispersion speed; adjusting the temperature in the reaction kettle and the ratio of the viscosity modifier according to the torsion of the screw rod; judging the mixing degree of the molten material in the reaction kettle according to the fluctuation condition of the torsion of the screw rod; the melting type of the molten material is judged according to the dispersion degree and the fluctuation condition of the torsion, and the feeding speed of the auxiliary materials is adjusted; and extruding, cooling and solidifying the molten material, and cutting the molten material into granular or strip-shaped hot melt adhesive. According to the method, the process parameters in the preparation process are accurately adjusted by judging the mixing degree of the molten materials.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and in particular to a hot melt adhesive with high bonding performance and a preparation method thereof. Background Art

[0002] Hot melt adhesive is an adhesive that can quickly melt and bond materials after heating, and form a strong bond after cooling. This adhesive is widely used in packaging, book binding, wood processing, automobile manufacturing, electronic product assembly and other fields. The method of using adhesives to achieve connection and retention: It is an important supplement to traditional mechanical connection methods such as welding, riveting, and bolting. It occupies a very important position in the fields of machinery, construction, electronics, aerospace, etc. The bonding process is simpler and easier to achieve. With the rapid development of modern polymer chemical industry, new synthetic adhesives are constantly emerging, making significant progress in bonding technology. Compared with natural adhesives, synthetic adhesives have more varieties, stronger bonding strength, better durability and wider applicability.

[0003] Chinese patent publication number: CN110055030A discloses a method for preparing a hot melt adhesive, wherein a base resin, a solid tackifier, etc. are pre-mixed according to a formula, and then fed from a solid feed port of an extensional rheological extruder, and a liquid plasticizer is weighed and added and heated to 80-120°C, and then plasticized, mixed and extruded through an extensional rheological extruder, and then pelletized and dried through a water ring to obtain a hot melt adhesive product; it can be seen that the method for preparing the hot melt adhesive has the following problems:

[0004] It is impossible to accurately judge whether the materials are evenly mixed and dispersed during the mixing process of high viscosity and low viscosity materials. Summary of the invention

[0005] To this end, the present invention provides a hot melt adhesive with high bonding performance and a preparation method thereof, so as to overcome the problem in the prior art that it is impossible to accurately judge whether the materials are evenly mixed and dispersed during the mixing process of materials with high viscosity differences.

[0006] To achieve the above object, the present invention provides a hot melt adhesive with high bonding performance and a preparation method thereof, comprising:

[0007] Step S1, adding a catalyst to ethylene and vinyl acetate at high temperature and high pressure to carry out copolymerization reaction to prepare ethylene-vinyl acetate copolymer, judging the melting state of the copolymer according to the melt flow rate, and adding the copolymers in different melting states as base materials into a reactor;

[0008] Step S2, mixing the tackifier, viscosity modifier, filler and antioxidant according to the initial proportion, and slowly adding them into the reactor as auxiliary materials through a peristaltic pump at an auxiliary material port at an initial feeding speed;

[0009] Step S3, a screw is provided in the reactor, and the base material and the auxiliary material are mixed and stirred by rotating the screw at an initial screw speed;

[0010] Step S4, detecting the actual dispersion degree of the auxiliary material in the base material according to the initial detection cycle, judging whether the mixing degree of the base material and the auxiliary material meets the standard, judging the mixing speed of the materials according to the dispersion speed of the auxiliary material in the base material, and adjusting the initial screw speed of the screw;

[0011] Step S5, detecting the torque of the screw in the reactor, determining the reason why the mixing speed of the materials does not meet the requirements, and adjusting the temperature in the reactor and the ratio of the viscosity regulator in the auxiliary materials;

[0012] Step S6, detecting the fluctuation of the screw torque in the reactor, and judging the mixing degree of the molten material in the reactor according to the fluctuation;

[0013] Step S7, judging the melting type of the molten material according to the fluctuation of the dispersion and the torque, and adjusting the initial feeding speed of the auxiliary material;

[0014] Step S8, extruding the molten material, cooling and solidifying it, and cutting it into particles or strips of hot melt adhesive.

[0015] Further, the process of judging the molten state of the copolymer according to the melt flow rate includes:

[0016] measuring the melt flow rate of the copolymer,

[0017] If the melt flow rate is less than the standard flow rate, the copolymer is judged to be in a first molten state;

[0018] If the melt flow rate is greater than or equal to the standard flow rate, the copolymer is judged to be in the second molten state;

[0019] The copolymer in the first molten state is divided into a first prepolymer, the copolymer in the second molten state is divided into a second copolymer, and the first prepolymer and the second copolymer are added into a reaction kettle as base materials.

[0020] Further, the rate difference between the melt flow rate and the standard flow rate is calculated. When the copolymer is in the first molten state, if the rate difference is greater than the rate difference evaluation value, it is judged that the heating temperature of the copolymer is low, and the heating temperature is increased according to the ratio of the rate difference to the rate difference evaluation value.

[0021] When the copolymer is in the second melting state, if the rate difference is greater than the rate difference evaluation value, it is judged that the copolymer has a large fluidity, and the content of vinyl acetate is reduced according to the ratio of the rate difference evaluation value to the rate difference.

[0022] Furthermore, the process of judging whether the mixing degree of the base material and the auxiliary material meets the standard includes:

[0023] According to the initial test cycle, the dispersion of auxiliary materials in the melt is measured.

[0024] If the dispersion is greater than or equal to the standard dispersion, it is judged that the dispersion of the molten mixed material in the reactor meets the standard;

[0025] If the dispersion is less than the standard dispersion, it is determined that the dispersion of the molten mixed material in the reactor does not meet the standard, the molten material continues to be mixed, and the mixing speed of the molten material is determined.

[0026] Further, the process of determining the mixing speed of the molten material includes,

[0027] The dispersion speed is calculated based on the dispersion of the current initial detection cycle and the historical initial detection cycle.

[0028] If the dispersion speed is greater than or equal to the standard dispersion speed, it is judged that the mixing speed of the molten material in the reactor is moderate;

[0029] If the dispersion speed is lower than the standard dispersion speed, it is judged that the mixing speed of the molten material in the reactor is slow, and the initial screw speed of the screw is increased according to the ratio of the standard dispersion speed to the dispersion speed.

[0030] Further, the reason why the molten material in the reactor is mixed slowly is determined.

[0031] Detect the torque of the screw in the reactor. If the torque of the screw is within the torque range, it is judged that the torque of the screw is moderate. The reason why the mixing speed of the molten material is slow is that the temperature in the reactor is not within the temperature range. Adjust the temperature in the reactor.

[0032] If the screw torque exceeds the torque range, it is judged that the reason for the slow mixing speed of the molten material is that the viscosity of the material in the reactor is relatively large, and the ratio of the viscosity regulator in the auxiliary material is increased.

[0033] Furthermore, the process of adjusting the temperature in the reactor includes:

[0034] Detect the material temperature in the reactor, draw a temperature change curve based on the material temperature, calculate the derivative of the curve, and analyze the change trend of the material temperature.

[0035] If the corresponding derivative function value on the temperature change curve is greater than zero, it is judged that the material temperature is rising and approaching the temperature range, and the cooling power of the cooling device is reduced according to the material temperature, the minimum critical temperature and the derivative function value;

[0036] If the corresponding derivative function value on the temperature change curve is less than zero, it is judged that the material temperature is continuously decreasing, and the cooling power of the cooling device is reduced according to the material temperature, the minimum critical temperature and the derivative function value;

[0037] The minimum critical temperature is the maximum and minimum values ​​of the temperature range set according to the properties of the hot melt adhesive material.

[0038] Further, the process of determining the degree of mixing of the molten material in the reactor includes:

[0039] According to the initial detection period, the actual torque of the screw in the reactor is measured, and the difference between the actual torque and the historical torque is calculated.

[0040] If the torque difference is less than the difference evaluation value, it is judged that the torque fluctuation is moderate and the degree of mixing of the molten material in the reactor is relatively uniform;

[0041] If the torque difference is greater than the difference evaluation value, it is determined that the molten material is not mixed uniformly in the reactor, and mixing and stirring are continued.

[0042] Furthermore, the process of determining the melting type of the molten material includes:

[0043] If the torque fluctuation is moderate and the dispersion is up to standard, it is judged that the melting category of the molten material is in the first melting category and the molten material in the reactor meets the standard requirements;

[0044] If the torque fluctuation is not moderate, or the dispersion is not up to standard, it is judged that the melting category of the molten material is in the second melting category, and the molten material in the reactor does not meet the standard requirements.

[0045] Furthermore, the process of adjusting the initial feeding speed of the auxiliary material includes:

[0046] When the molten material in the reactor reaches the standard requirements, the initial feeding speed of the auxiliary materials is increased according to the initial increase coefficient.

[0047] If the actual dispersion is greater than or equal to the standard dispersion or the torque difference is less than or equal to the difference evaluation value, the initial amplification coefficient is judged to be moderate;

[0048] If the actual dispersion is less than the standard dispersion or the torque difference is greater than the difference evaluation value, the initial amplification coefficient is judged to be large, and the initial amplification coefficient is reduced according to the ratio of the actual dispersion to the standard dispersion or the ratio of the difference evaluation value to the torque difference.

[0049] Compared with the prior art, the beneficial effects of the present invention are that the melt flow rate (MFR, melt mass flow rate), also referred to as the melt index (MI), is the number of grams of molten resin flowing out through a standard capillary within a certain time (generally 10 minutes) under a certain temperature and pressure in a standardized melt indexer; the melting state of the copolymer is judged by the melt flow rate, and copolymers in different melting states are added to the reactor to increase the shear force between the fluids during stirring, improve the uniformity of mixing, and promote the reaction rate; the fluidity difference of the copolymers in different melting states is judged by the rate difference, and the heating temperature and the content of vinyl acetate are adjusted to avoid excessive difference in the fluidity of the copolymers.

[0050] Furthermore, the mixing speed of the molten mixed material in the reactor is determined according to the dispersion speed of the auxiliary material in the base material, and timely measures are taken to improve the accuracy of judging the process parameters of the hot melt adhesive production process; the screw torque is affected by the viscosity of the material. The reason for the low screw speed is determined by the screw torque, and the temperature in the reactor is adjusted or the ratio of the viscosity regulator in the auxiliary material is increased to reduce the viscosity of the material, thereby increasing the mixing speed of the molten mixed material and improving production efficiency.

[0051] Furthermore, during the production process, the heating temperature needs to be precisely controlled to ensure that the hot melt adhesive is at an appropriate viscosity and fluidity. Too high a temperature may cause the adhesive to flow excessively and degrade, while too low a temperature may make the adhesive too dense, affecting its adhesion. Therefore, it is necessary to select a suitable temperature range and make precise adjustments according to production needs. When the material temperature is continuously decreasing, the degree of reduction in the cooling power of the cooling device is increased; when the material temperature is rising and approaching the temperature range, the degree of reduction in the cooling power of the cooling device is reduced.

[0052] Furthermore, the mixing degree of the materials in the reactor directly affects the torsion exerted on the screw. When the materials are mixed unevenly, there are differences in the viscosity of the materials flowing in the reactor, which have different effects on the torsion exerted on the screw. The screw torsion varies in size, resulting in fluctuations in the screw torsion. The present invention determines the mixing degree of the molten materials in the reactor by judging the volatility of the screw torsion, ensures that the auxiliary materials are evenly distributed in the base material of the reactor, thereby improving the uniformity of the reaction between the base material and the auxiliary materials, accelerating the contact and reaction rate between the reactants, shortening the reaction time, ensuring the uniformity of the product ingredients, and improving the product quality.

[0053] Furthermore, in the prior art, the reaction time is generally used to judge whether the molten material in the reactor meets the standard requirements, but the reaction time is affected by many factors, such as reaction temperature, concentration of reaction materials, stirring speed of the reactor, etc. Changes in these factors will affect the reaction time, thereby affecting the accuracy of the judgment; the present invention judges whether the molten material meets the standard requirements through the dispersion of the base material in the auxiliary material in the reactor and the volatility of the screw torque, thereby ensuring that the quality and performance of the prepared hot melt adhesive meet the requirements, increasing the initial feeding speed of the auxiliary material through the initial amplification coefficient, optimizing the process parameters, and improving the preparation speed and overall production efficiency of the hot melt adhesive.

[0054] Furthermore, when the colloid is melted at a high temperature, it will oxidize and decompose. Adding an antioxidant can ensure that the bonding properties do not change under high temperature conditions; adding a tackifier can increase the fluidity of the colloid and its wettability to the adherend, improve the bonding properties, and achieve the required bonding strength; viscosity regulator is also one of the main additives of hot melt adhesive. Its function is to increase the fluidity of the colloid and adjust the solidification speed to achieve the purpose of rapid and firm bonding; fillers can increase the hardness of the hot melt adhesive and reduce the linear expansion coefficient, thereby improving the physical properties of the hot melt adhesive. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of a process for preparing a hot melt adhesive with high bonding performance according to an embodiment of the present invention;

[0056] Figure 2 Schematic diagram of a process for determining the melting state of a copolymer according to the melt flow rate in an embodiment of the present invention;

[0057] Figure 3 The present invention is a schematic diagram of a process for judging whether the mixing degree of the base material and the auxiliary material meets the standard according to the dispersion degree in an embodiment of the present invention;

[0058] Figure 4 It is a schematic diagram of a flow chart for judging the reason why the screw speed is low according to the screw torque in an embodiment of the present invention; DETAILED DESCRIPTION

[0059] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0060] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0061] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0062] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] See also Figure 1-Figure 4 As shown,

[0065] The present invention provides a method for preparing a hot melt adhesive with high bonding performance, comprising:

[0066] Step S1, adding a catalyst to ethylene and vinyl acetate at high temperature and high pressure to carry out copolymerization reaction to prepare ethylene-vinyl acetate copolymer, judging the melting state of the copolymer according to the melt flow rate, and adding the copolymers in different melting states as base materials into a reactor;

[0067] Step S2, mixing the tackifier, viscosity modifier, filler and antioxidant according to the initial proportion, and slowly adding them into the reactor as auxiliary materials through a peristaltic pump at an auxiliary material port at an initial feeding speed;

[0068] Step S3, a screw is provided in the reactor, and the base material and the auxiliary material are mixed and stirred by rotating the screw at an initial screw speed;

[0069] Step S4, detecting the actual dispersion degree of the auxiliary material in the base material according to the initial detection cycle, judging whether the mixing degree of the base material and the auxiliary material meets the standard, judging the mixing speed of the materials according to the dispersion speed of the auxiliary material in the base material, and adjusting the initial screw speed of the screw;

[0070] Step S5, detecting the torque of the screw in the reactor, determining the reason why the mixing speed of the materials does not meet the requirements, and adjusting the temperature in the reactor and the ratio of the viscosity regulator in the auxiliary materials;

[0071] Step S6, detecting the fluctuation of the screw torque in the reactor, and judging the mixing degree of the molten material in the reactor according to the fluctuation;

[0072] Step S7, judging the melting type of the molten material according to the fluctuation of the dispersion and the torque, and adjusting the initial feeding speed of the auxiliary material;

[0073] Step S8, extruding the mixed material through an extruder, and cutting it into granules or strips of hot melt adhesive after cooling and solidification.

[0074] The tackifier is one or more of rosin ester and terpene resin; the antioxidant is one of antioxidant DLTP antioxidant 1010; the viscosity regulator is one of paraffin and microcrystalline wax or a mixture of the two; the filler is one of calcium carbonate and talcum powder.

[0075] Specifically, EVA resin is a copolymer of ethylene and vinyl acetate under high temperature and high pressure. This resin is the main component of hot melt adhesive. The proportion and quality of the basic resin determine the basic properties of the hot melt adhesive. In this embodiment, ethylene-vinyl acetate copolymer with a VA content of 18-33% and a melt index (MI) of 6-800 is selected.

[0076] In step S1, the melt flow rate of the copolymer is measured using a melt indexer, and the melting state of the copolymer is determined according to the melt flow rate.

[0077] If the melt flow rate is less than the standard flow rate, the copolymer is judged to be in a first molten state;

[0078] If the melt flow rate is greater than or equal to the standard flow rate, the copolymer is judged to be in the second molten state.

[0079] Wherein, the rate difference between the melt flow rate and the standard flow rate is calculated, and when the copolymer is in the first melting state, if the rate difference is greater than the rate difference evaluation value, it is judged that the heating temperature of the copolymer is low, and the heating temperature is increased according to the ratio of the rate difference to the rate difference evaluation value;

[0080] When the copolymer is in the second melting state, if the rate difference is greater than the rate difference evaluation value, it is judged that the copolymer has a large fluidity, and the content of vinyl acetate is reduced according to the ratio of the rate difference evaluation value to the rate difference.

[0081] Specifically, the copolymers in different molten states are divided into a first prepolymer and a second copolymer, and the first prepolymer and the second copolymer are added into a reaction kettle as base materials.

[0082] The first prepolymer is a copolymer in a first molten state, the second copolymer is a copolymer in a second molten state, and the copolymer is an ethylene-vinyl acetate copolymer;

[0083] Wherein, the speed difference evaluation value is a preset value set according to the error value of the standard flow rate of the copolymer in the historical data;

[0084] In practice, the actual implementers may determine the standard flow rate according to the actual situation or based on the melt flow rate of the copolymer that has passed the qualification test in historical data.

[0085] Specifically, the melt flow rate (MFR, melt mass flow rate), also referred to as the melt index (MI), is the number of grams of molten resin flowing out through a standard capillary within a certain period of time (generally 10 minutes) under a certain temperature and pressure in a standardized melt indexer; the melt state of the copolymer is judged by the melt flow rate, and copolymers in different melt states are added to the reactor to increase the shear force between the fluids during stirring, improve the uniformity of mixing, and promote the reaction rate; the fluidity difference of copolymers in different melt states is judged by the rate difference, and the heating temperature and the content of vinyl acetate are adjusted to avoid excessive differences in the fluidity of the copolymers.

[0086] Use a dynamic light scattering instrument to measure the actual dispersion of the auxiliary materials in the base material according to the initial test cycle, and determine whether the mixing degree of the base material and the auxiliary materials meets the standard based on the actual dispersion.

[0087] If the actual dispersion is greater than or equal to the standard dispersion, it is judged that the dispersion of the molten mixed material in the reactor meets the standard;

[0088] If the actual dispersion is less than the standard dispersion, it is determined that the dispersion of the molten mixed material in the reactor does not meet the standard, the molten material continues to be mixed, and the mixing speed of the molten material is determined.

[0089] Calculate the dispersion speed of the dispersion degree according to the actual dispersion degree detected in the current initial detection period and the historical initial detection period;

[0090] In implementation, the dispersion speed is calculated based on the ratio of the absolute value of the difference between the actual dispersion detected in the current initial detection cycle and the historical initial detection cycle to the initial detection cycle;

[0091] If the dispersion speed is greater than or equal to the standard dispersion speed, it is judged that the mixing speed of the molten mixed material in the reactor is moderate;

[0092] If the dispersion speed is lower than the standard dispersion speed, it is judged that the mixing speed of the molten mixed material in the reactor is slow. The reason for the slow mixing speed is that the screw speed in the reactor is low. Increase the initial screw speed of the screw according to the ratio of the standard dispersion speed to the dispersion speed.

[0093] In practice, the actual implementer may determine the standard dispersion degree and standard dispersion speed according to the actual situation or based on the minimum dispersion degree and the minimum dispersion speed of the mixed molten material that has passed the qualification test in historical data.

[0094] Detect the torque of the screw in the reactor and determine the reason for the low screw speed.

[0095] If the screw torque is within the torque range, it is judged that the screw torque is moderate. The reason why the screw speed is low is that the temperature in the reactor is not within the temperature range. Adjust the temperature in the reactor.

[0096] If the screw torque exceeds the torque range, it is judged that the reason for the low screw speed is that the viscosity of the material in the reactor is relatively large, and the proportion of the viscosity regulator in the auxiliary material is increased.

[0097] Specifically, the torque range and temperature range are preset ranges set according to the temperature in the reactor and the screw torque during the preparation process of the hot melt adhesive that has passed the qualification test in historical data.

[0098] Specifically, the mixing speed of the molten mixed material in the reactor is determined according to the dispersion speed of the auxiliary material in the base material, and timely measures are taken to improve the accuracy of judging the process parameters of the hot melt adhesive production process; the screw torque is affected by the viscosity of the material. The reason for the low screw speed can be determined by the screw torque, and the temperature in the reactor can be adjusted or the ratio of the viscosity regulator in the auxiliary material can be increased to reduce the viscosity of the material, thereby increasing the mixing speed of the molten mixed material and improving production efficiency.

[0099] Adjust the temperature in the reactor.

[0100] Use a temperature sensor to detect the material temperature in the reactor, draw a temperature change curve based on the material temperature, and calculate the derivative of the curve.

[0101] If the temperature value corresponding to any moment on the temperature change curve is less than or equal to the minimum critical temperature, it is judged that the material temperature is lower than the temperature range, and the cooling power of the cooling device is reduced according to the ratio of the material temperature to the minimum critical temperature;

[0102] And analyze the changing trend of material temperature,

[0103] If the corresponding derivative function value on the temperature change curve is greater than zero, it is judged that the material temperature is rising and approaching the temperature range, and the cooling power of the cooling device is reduced according to the material temperature, the minimum critical temperature and the derivative function value;

[0104] In implementation, the cooling power of the cooling device is reduced according to the product of the ratio of the material temperature to the minimum critical temperature and the derivative function value.

[0105] If the corresponding derivative function value on the temperature change curve is less than zero, it is judged that the material temperature is continuously decreasing, and the cooling power of the cooling device is reduced according to the material temperature, the minimum critical temperature and the derivative function value;

[0106] In implementation, the cooling power of the cooling device is reduced according to the quotient of the ratio of the material temperature to the minimum critical temperature and the absolute value of the derivative function value.

[0107] The minimum critical temperature is the maximum and minimum values ​​of the temperature range set according to the properties of the hot melt adhesive material.

[0108] Specifically, during the production process, the heating temperature needs to be precisely controlled to ensure that the hot melt adhesive is at the appropriate viscosity and fluidity. Too high a temperature may cause the adhesive to flow excessively and degrade, while too low a temperature will make the adhesive too dense, affecting its adhesion. Therefore, it is necessary to select a suitable temperature range and make precise adjustments according to production needs. When the material temperature is continuously decreasing, increase the degree of reduction in the cooling power of the cooling device; when the material temperature is rising and approaching the temperature range, reduce the degree of reduction in the cooling power of the cooling device.

[0109] Detect the fluctuation of the screw torque in the reactor and judge the mixing degree of the molten material in the reactor according to the fluctuation;

[0110] According to the initial detection period, the actual torque of the screw in the reactor is measured, and the difference between the actual torque and the historical torque is calculated.

[0111] If the torque difference is less than the difference evaluation value, it is judged that the torque fluctuation is moderate and the degree of mixing of the molten material in the reactor is relatively uniform;

[0112] If the torque difference is greater than the difference evaluation value, it is judged that the torque fluctuation is large and the mixing degree of the molten material in the reactor is uneven, and the mixing and stirring continues.

[0113] Specifically, the difference evaluation value is a preset value set according to the difference between the actual torque and the historical torque in the historical data.

[0114] Specifically, the mixing degree of the materials in the reactor directly affects the torsion exerted on the screw. When the materials are mixed unevenly, the viscosity of the materials flowing in the reactor varies, which has different effects on the torsion exerted on the screw. The screw torsion varies in size, resulting in fluctuations in the screw torsion. The present invention determines the mixing degree of the molten materials in the reactor by judging the volatility of the screw torsion, ensures that the auxiliary materials are evenly distributed in the base material of the reactor, thereby improving the uniformity of the reaction between the base material and the auxiliary materials, accelerating the contact and reaction rate between the reactants, shortening the reaction time, ensuring the uniformity of the product ingredients, and improving the product quality.

[0115] Determine whether the molten material meets the demand and adjust the initial feeding speed of the auxiliary materials;

[0116] If the torque fluctuation is moderate and the dispersion is up to standard, it is judged that the melting category of the molten material is in the first melting category and the molten material in the reactor meets the standard requirements;

[0117] If the torque fluctuation is not moderate, or the dispersion is not up to standard, it is judged that the melting category of the molten material is in the second melting category, and the molten material in the reactor does not meet the standard requirements.

[0118] When the molten material in the reactor reaches the standard requirements, the initial feeding speed of the auxiliary materials is increased according to the initial increase coefficient.

[0119] After increasing the initial feeding speed of auxiliary materials according to the initial increase coefficient,

[0120] If the actual dispersion is greater than or equal to the standard dispersion or the torque difference is less than or equal to the difference evaluation value, the initial amplification coefficient is judged to be moderate;

[0121] If the actual dispersion is less than the standard dispersion or the torque difference is greater than the difference evaluation value, the initial amplification coefficient is judged to be large, and the initial amplification coefficient is reduced according to the ratio of the actual dispersion to the standard dispersion or the ratio of the difference evaluation value to the torque difference.

[0122] In implementation, the initial amplification factor is determined according to the ratio of the dispersion of the molten material in the first melting category to the standard dispersion or the ratio of the difference evaluation value to the torque difference.

[0123] Specifically, in the prior art, the reaction time is generally used to judge whether the molten material in the reactor meets the standard requirements, but the reaction time is affected by many factors, such as reaction temperature, concentration of reaction materials, stirring speed of the reactor, etc. Changes in these factors will affect the reaction time, thereby affecting the accuracy of the judgment; the present invention judges whether the molten material meets the standard requirements through the dispersion of the base material in the auxiliary material in the reactor and the volatility of the screw torque, ensures that the quality and performance of the prepared hot melt adhesive meet the requirements, increases the initial feeding speed of the auxiliary material through the initial amplification coefficient, optimizes the process parameters, and improves the preparation speed of the hot melt adhesive and the overall production efficiency.

[0124] A hot melt adhesive with high bonding performance, characterized in that:

[0125] Using ethylene-vinyl acetate copolymer in a first molten state and a second molten state as a base material;

[0126] The tackifier, viscosity modifier, filler and antioxidant are mixed according to the initial proportion as auxiliary materials.

[0127] Specifically, when the colloid is melted at a high temperature, it will oxidize and decompose. Adding an antioxidant can ensure that the bonding properties do not change under high temperature conditions; adding a tackifier can increase the fluidity of the colloid and its wettability to the adherend, improve the bonding properties, and achieve the required bonding strength; viscosity regulator is also one of the main additives of hot melt adhesive. Its function is to increase the fluidity of the colloid and adjust the solidification speed to achieve the purpose of rapid and firm bonding; fillers can increase the hardness of the hot melt adhesive and reduce the linear expansion coefficient, thereby improving the physical properties of the hot melt adhesive.

[0128] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a hot melt adhesive with high bonding performance, characterized in that: include: Step S1, adding a catalyst to ethylene and vinyl acetate at high temperature and high pressure to carry out copolymerization reaction to prepare ethylene-vinyl acetate copolymer, judging the melting state of the copolymer according to the melt flow rate, and adding the copolymers in different melting states as base materials into a reactor; Step S2, mixing the tackifier, viscosity modifier, filler and antioxidant according to the initial proportion, and slowly adding them into the reactor as auxiliary materials through a peristaltic pump at an auxiliary material port at an initial feeding speed; Step S3, a screw is provided in the reactor, and the base material and the auxiliary material are mixed and stirred by rotating the screw at an initial screw speed; Step S4, detecting the actual dispersion degree of the auxiliary material in the base material according to the initial detection cycle, judging whether the mixing degree of the base material and the auxiliary material meets the standard, judging the mixing speed of the materials according to the dispersion speed of the auxiliary material in the base material, and adjusting the initial screw speed of the screw; Step S5, detecting the torque of the screw in the reactor, determining the reason why the mixing speed of the materials does not meet the requirements, and adjusting the temperature in the reactor and the ratio of the viscosity regulator in the auxiliary materials; Step S6, detecting the fluctuation of the screw torque in the reactor, and judging the mixing degree of the molten material in the reactor according to the fluctuation; Step S7, judging the melting type of the molten material according to the fluctuation of the dispersion and the torque, and adjusting the initial feeding speed of the auxiliary material; Step S8, extruding the molten material, cooling and solidifying it, and cutting it into particles or strips of hot melt adhesive.

2. The method for preparing a hot melt adhesive with high bonding performance according to claim 1, characterized in that: The process of judging the molten state of a copolymer based on the melt flow rate includes: Measuring the melt flow rate of the copolymer, and if the melt flow rate is less than the standard flow rate, determining that the copolymer is in a first molten state; If the melt flow rate is greater than or equal to the standard flow rate, the copolymer is judged to be in the second molten state; dividing the copolymer in a first molten state into a first prepolymer, dividing the copolymer in a second molten state into a second copolymer, and adding the first prepolymer and the second copolymer as base materials into a reaction kettle; Calculate the rate difference between the melt flow rate and the standard flow rate. When the copolymer is in the first melting state, if the rate difference is greater than the rate difference evaluation value, it is judged that the heating temperature of the copolymer is low, and the heating temperature is increased according to the ratio of the rate difference to the rate difference evaluation value. When the copolymer is in the second melting state, if the rate difference is greater than the rate difference evaluation value, it is judged that the copolymer has a large fluidity, and the content of vinyl acetate is reduced according to the ratio of the rate difference evaluation value to the rate difference.

3. The method for preparing a hot melt adhesive with high bonding performance according to claim 1, characterized in that: The process of judging whether the mixing degree of base material and auxiliary material meets the standard includes: According to the initial detection cycle, the actual dispersion of the auxiliary material in the melt is measured. If the actual dispersion is greater than or equal to the standard dispersion, it is judged that the dispersion of the molten mixed material in the reactor meets the standard; If the actual dispersion is less than the standard dispersion, it is determined that the dispersion of the molten mixed material in the reactor does not meet the standard, the molten material continues to be mixed, and the mixing speed of the molten material is determined.

4. The method for preparing a hot melt adhesive with high bonding performance according to claim 3, characterized in that: The process of determining the mixing rate of the molten material includes, The dispersion speed is calculated based on the dispersion of the current initial detection cycle and the historical initial detection cycle. If the dispersion speed is greater than or equal to the standard dispersion speed, it is judged that the mixing speed of the molten material in the reactor is moderate; If the dispersion speed is lower than the standard dispersion speed, it is judged that the mixing speed of the molten material in the reactor is slow, and the initial screw speed of the screw is increased according to the ratio of the standard dispersion speed to the dispersion speed.

5. The method for preparing a hot melt adhesive with high bonding performance according to claim 4, characterized in that: Determine the reason why the molten materials in the reactor are mixed slowly. Detect the torque of the screw in the reactor. If the torque of the screw is within the torque range, it is judged that the torque of the screw is moderate. The reason why the mixing speed of the molten material is slow is that the temperature in the reactor is not within the temperature range. Adjust the temperature in the reactor. If the screw torque exceeds the torque range, it is judged that the reason for the slow mixing speed of the molten material is that the viscosity of the material in the reactor is relatively large, and the ratio of the viscosity regulator in the auxiliary material is increased.

6. The method for preparing a hot melt adhesive with high bonding performance according to claim 5, characterized in that: The process of regulating the temperature in the reactor includes: Detect the material temperature in the reactor, draw a temperature change curve based on the material temperature, calculate the derivative of the curve, and analyze the change trend of the material temperature. If the corresponding derivative function value on the temperature change curve is greater than zero, it is judged that the material temperature is rising and approaching the temperature range, and the cooling power of the cooling device is reduced according to the material temperature, the minimum critical temperature and the derivative function value; If the corresponding derivative function value on the temperature change curve is less than zero, it is judged that the material temperature is continuously decreasing, and the cooling power of the cooling device is reduced according to the material temperature, the minimum critical temperature and the derivative function value; The minimum critical temperature is the maximum and minimum values ​​of the temperature range set according to the properties of the hot melt adhesive material.

7. The method for preparing a hot melt adhesive with high bonding performance according to claim 1, characterized in that: The process of determining the degree of mixing of the molten material in the reactor includes: According to the initial detection period, the actual torque of the screw in the reactor is measured, and the difference between the actual torque and the historical torque is calculated. If the torque difference is less than the difference evaluation value, it is judged that the torque fluctuation is moderate and the mixing degree of the molten material in the reactor is relatively uniform; If the torque difference is greater than the difference evaluation value, it is determined that the molten material is not mixed uniformly in the reactor, and mixing and stirring are continued.

8. The method for preparing a hot melt adhesive with high bonding performance according to claim 1, characterized in that: The process of determining the melting type of the molten material includes: If the torque fluctuation is moderate and the dispersion is up to standard, it is judged that the melting category of the molten material is in the first melting category and the molten material in the reactor meets the standard requirements; If the torque fluctuation is not moderate, or the dispersion is not up to standard, it is judged that the melting category of the molten material is in the second melting category, and the molten material in the reactor does not meet the standard requirements.

9. The method for preparing a hot melt adhesive with high bonding performance according to claim 8, characterized in that: The process of adjusting the initial feeding speed of auxiliary materials includes: When the molten material in the reactor reaches the standard requirements, the initial feeding speed of the auxiliary materials is increased according to the initial increase coefficient. If the actual dispersion is greater than or equal to the standard dispersion or the torque difference is less than or equal to the difference evaluation value, the initial amplification coefficient is judged to be moderate; If the actual dispersion is less than the standard dispersion or the torque difference is greater than the difference evaluation value, the initial amplification coefficient is judged to be large, and the initial amplification coefficient is reduced according to the ratio of the actual dispersion to the standard dispersion or the ratio of the difference evaluation value to the torque difference.

10. A hot melt adhesive with high bonding performance, prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The hot melt adhesive uses ethylene-vinyl acetate copolymer in a first molten state and a second molten state as a base material; and uses a tackifier, a viscosity modifier, a filler and an antioxidant mixed in an initial proportion as auxiliary materials.

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