The invention content is as follows:
the invention aims to overcome the defects of the prior art and provide an industrialized pure PU foam alcoholysis recovery method.
Another object of the present invention is to provide a recycling and feeding device for alcoholysis of industrial pure PU foam.
The invention mainly solves the problems that the existing industrialized pure PU foam is slow in recovery and feeding, the VOC index of the polyalcohol is high and the like.
The technical scheme of the invention is as follows: an industrialized pure PU foam alcoholysis recovery method is characterized in that a special recovery feeding device is adopted, and the alcoholysis recovery method comprises the following process steps:
a, introducing dry nitrogen to exhaust air in a reaction kettle, adding a main alcoholysis agent and a catalyst into the reaction kettle, wherein the addition amount of the catalyst accounts for 0.1-0.12% of the total mass of the recovered polyol; weighing pure PU foam crushed aggregates needing to be recycled through a weighing bin, and conveying the pure PU foam crushed aggregates into a feeding hopper connected with a flexible connector through a screw conveyor;
b, extruding pure PU foam crushed aggregates temporarily stored in a feeding hopper into the main feeding screw conveyor through a plurality of rows of spirally arranged feeding teeth in a relatively rotating manner by an auxiliary feeding double-spiral feeding conveyor which operates later than the screw conveyor;
c, the main feeding screw conveyer pushes the extruded pure PU foam crushed aggregates into a feeding reducing elbow, and the diameter of the interface of the feeding reducing elbow and the main feeding screw conveyer is smaller than that of the interface of the feeding reducing elbow and the pneumatic gate valve; then PU foam crushed aggregates rapidly enter a feeding hole of a pneumatic gate valve which is opened simultaneously;
d, rapidly feeding the pure PU foam crushed aggregates into the reaction kettle through a feeding hole in a movable valve core of the pneumatic gate valve to finish the feeding process of the pure PU foam crushed aggregates at one time; adding pure PU foam crushed aggregates into the polyol by times, and correspondingly adding hexamethylenetetramine into the polyol by times through a small-aggregate feeding device, wherein the total mass of the hexamethylenetetramine added accounts for 0.13-0.15% of the total mass of the recycled polyol; after the feeding is finished each time, the movable valve core of the pneumatic gate valve is quickly reset, the movable valve core part without the feeding hole is communicated with the reaction kettle in a sealed way, and the polyol steam in the reaction kettle is prevented from overflowing;
e, adding the pure PU foam crushed aggregates and the main alcoholysis agent in a mass ratio of 46-48: 54-52; after the pure PU foam crushed aggregates are fed, carrying out recovery reaction at the temperature of 160-190 ℃ until all pure PU foam in the reaction kettle is completely alcoholyzed;
and f, after alcoholysis is completed, cooling the inside of the reaction kettle to 70-75 ℃, adding hydrogen peroxide into the reaction kettle once through the bottom of the small material feeding device, wherein the adding amount of the hydrogen peroxide is 0.40-0.43% of the total mass of the recovered polyol, continuously stirring for reaction for 1 hour, completely reacting aldehyde substances in the recovered polyol, heating the reaction kettle to 115-125 ℃, controlling the outlet temperature of the condensation reflux device and the water separation device to be 105-110 ℃, continuously stirring by a stirrer of the reaction kettle, removing generated water for about 1 hour under the drive of dry nitrogen until the water content of the recovered polyol is below 0.1%, cooling to 80-90 ℃, filtering by a 60-mesh stainless steel filter screen, discharging, and finishing the primary polyol recovery production process.
Further, the main alcoholysis agent in the step a is one or a mixture of two or more of ethylene glycol, 1, 4-butanediol, diethylene glycol, dipropylene glycol and polyethylene glycol 400.
Further, the catalyst in the step a is prepared from t-12 and triethylene diamine.
The invention relates to a special recovery feeding device for alcoholysis of industrial pure PU foam, which comprises a weighing bin and a screw conveyor, wherein the weighing bin and the screw conveyor are connected; the device is characterized in that the screw conveyor is connected with a feeding funnel through a flexible connection 7, an auxiliary feeding double-helix feeding conveyor is arranged below the feeding funnel and connected with a main feeding screw conveyor, the main feeding screw conveyor is connected with a feeding reducing elbow, and the feeding reducing elbow is communicated with a reaction kettle through a pneumatic gate valve; and the reaction kettle is provided with a small material feeding device.
Furthermore, the auxiliary feeding double-screw feeding conveyor runs later than the screw conveyor.
Furthermore, the diameter of the interface between the feeding reducing elbow and the main feeding screw conveyor is smaller than that of the interface between the feeding reducing elbow and the pneumatic gate valve.
Furthermore, the inner wall of the feeding reducing elbow is polished and sprayed with a Teflon coating layer, and the surface energy of the inner wall is lower than 20 dyn/cm.
Furthermore, the pneumatic gate valve is connected with the reaction kettle by a flange.
Furthermore, a polytetrafluoroethylene sealing gasket is used for self-lubricating sealing between the movable valve core and the fixed valve shell of the pneumatic gate valve.
Furthermore, the small material feeding device consists of a feeding hopper, a valve and a pipeline.
The comparative tests were as follows:
test 1, selecting a 3-ton reaction kettle, introducing dry nitrogen to exhaust air in the reaction kettle under the feeding conditions of a pneumatic gate valve 2, a feeding reducing elbow 3, a main feeding screw conveyor 4, an auxiliary feeding double-screw feeding conveyor 5, a feeding hopper 6 and a flexible connection 7, conveying 40 parts of diethylene glycol and 12 parts of polyethylene glycol 400 into the reaction kettle through a feeding pump, adding one part of triethylene diamine and one part of t-12, adding 46 parts of pure PU foam crushed aggregates in portions, raising the temperature in the reaction kettle to 175 ℃, stirring at a speed of 180r/min, adding about 900KG of pure PU foam crushed aggregates into the reaction kettle every time at a speed of 15KG/min for about 1h, continuing to react for 4h after stopping the pure PU foam, cooling to 80-90 ℃, filtering through a 60-mesh stainless steel filter screen, a tan-colored recovered product was obtained. The detection shows that the hydroxyl value is 386mgKOH/g, the water content is 0.086 percent, the recycled polyol is added into a foaming system according to the proportion, and the obtained PU plate has the following odor VOC detection:
comparing 1, selecting a 3-ton reaction kettle, wherein under the existing feeding condition, a pneumatic gate valve, a feeding reducing elbow, a main feeding screw conveyor, an auxiliary feeding double-screw feeding conveyor and a feeding hopper are not arranged, PU foam crushed aggregate weighing bins are only used for feeding the screw conveyor to the feeding hopper of the reaction kettle, the screw conveyor is directly communicated to a phi 300 pneumatic butterfly valve through flexible connection, and the feeding speed can reach 5KG/min at most, and sometimes the feeding is influenced by the blockage of the pneumatic butterfly valve; only the pure PU foam particles required are fed into the reaction kettle for more than 3 hours; and (3) feeding pure PU foam crushed aggregates, reacting for 2 hours, cooling to 80-90 ℃, and filtering by a stainless steel filter screen of 60 meshes to obtain a tan recovered product. The detection shows that the hydroxyl value is 390mgKOH/g, the water content is 0.096%, the recycled polyol is added into a foaming system in proportion, and the obtained PU plate has the following odor VOC detection:
compared with the control 1, under the same other conditions, the feeding time of each polyol recovery is shortened from 3h to 1h under the same conditions only because of different feeding devices of the reaction kettle; under the same long-time condition, the feeding efficiency of pure PU foam crushed aggregates is improved by more than 3 times; as the pure PU foam crushing efficiency is improved in the test 1, the reaction time is relatively prolonged, the moisture content index is obviously reduced by about 12 percent, but the hydroxyl value index and the important odor index of the recycled polyol are not obviously improved, and therefore, the process production needs to be continuously improved.
Experiment 2, selecting a 3-ton reaction kettle, introducing dry nitrogen to exhaust air in the reaction kettle 1 under the feeding condition of a pneumatic gate valve 2, a feeding reducing elbow 3, a main feeding screw conveyor 4, an auxiliary feeding double-screw feeding conveyor 5, a feeding hopper 6 and a flexible connection 7, conveying 40 parts of diethylene glycol and 12 parts of polyethylene glycol 400 into the reaction kettle through a feeding pump, adding one part of triethylene diamine and one part of t-12, adding 46 parts of pure PU foam crushed aggregates in a fractional manner, raising the temperature in the reaction kettle to 175 ℃, stirring at the speed of 180r/min, feeding 15KG/min into the reaction kettle at each time, adding hexamethylenetetramine in a fractional manner corresponding to a small feeding hopper and a feeding valve pipeline 8 of the reaction kettle in the process of adding pure PU foam in a fractional manner through a small feeding hopper and a feeding valve pipeline 8 of the reaction kettle, the total amount of the added components accounts for 0.13-0.15% of the total amount of the recycled polyol. And (3) continuously reacting for 2 hours at constant temperature after the pure PU foam crushed aggregates are added for the last time, cooling to 70-75 ℃, adding 30% of hydrogen peroxide through a small-material feeding hopper and a feeding valve pipeline 8 of the reaction kettle, wherein the total amount of the hydrogen peroxide accounts for 0.40-0.42% of the total amount of the recovered polyol. And after continuously stirring and reacting for 1h, heating the reaction kettle to 115-125 ℃, controlling the outlet temperature of the condensation reflux device and the water separation device to be 105-110 ℃, and removing water for more than 1h under the driving of dry nitrogen under the condition that the stirring of the stirring machine of the reaction kettle is continuously performed until the water content of the polyhydric alcohol is removed to be below 0.1 percent through detection. Cooling to 80-90 ℃, testing the polyol recovered after being filtered by a 60-mesh stainless steel net, wherein the hydroxyl value is 336mgKOH/g, the water content is 0.88%, adding the recovered polyol into a foaming system in proportion, and detecting the VOC (volatile organic compounds) of the obtained PU plate as follows:
comparing 2, under the condition that a small material feeding device 8 of the reaction kettle is not used, adding a catalyst into the reaction kettle along with a main alcoholysis agent at one time, adding no hexamethylenetetramine and hydrogen peroxide, continuously reacting for 2 hours at constant temperature after adding pure PU foam crushed aggregates at the last time, delaying the reaction for 2 hours, cooling to 80-90 ℃, testing the polyol recovered after filtering through a 60-mesh stainless steel net, wherein the hydroxyl value is 398mgKOH/g, the water content is 0.087%, adding the recovered polyol into a foaming system according to the proportion, and detecting the VOC of the obtained PU plate by using the recovered polyol:
through comparison between the experiment 2 and the comparison 2, feeding is carried out under the condition that a special device for a pure PU foam alcoholysis recovery reaction kettle is arranged, and through improvement of a recovery process, in a recovery process (5 h) which is basically the same for a long time, aldehyde substances in the recovered polyol are basically reacted, the hydroxyl value index is reduced by about 18%, and the comparison of an odor VOC project is obviously improved; the odor is reduced by 0.5 grade according to the public standard, and the odor is reduced by 1 grade according to the Jili standard; and the reduction of the VOC index content of the recycled polyol is the key for successfully recycling the pure PU foam waste leftover material.
Compared with the water content of the control 1, the water content of the recovered polyol is obviously reduced by 9-12% by comparing the water content of the test 1 and the test 2, which indicates that the pure PU foam is fed quickly for reaction, and the recovered polyol is dehydrated for a longer time to help reduce the water content; the invention improves the quality of the recycled polyol and enlarges the application range of the recycled polyol.
Through comparison of tests and controls, the recovery and feeding device and the recovery process provided by the invention can be used for recovering and producing pure PU foam, and the quality of the obtained recovered polyol is obviously improved.
Compared with the prior art, the industrialized pure PU foam alcoholysis recovery method and the special recovery feeding device thereof have prominent substantive characteristics and remarkable progress: 1. in the PU foam feeding process, hexamethylenetetramine is added from a small material feeding device of a reaction kettle, aromatic amine generated in the polyol recovery reaction process is converted into aldehyde substances and ammonia gas, the ammonia gas is discharged out of the reaction system along with nitrogen gas, and the aldehyde substances are required to be further treated; 2. after the recovery reaction of the polyhydric alcohol is finished, adding hydrogen peroxide into the reaction kettle through a small material feeding device at a certain temperature, reacting with the aldehyde substance, oxidizing the aldehyde substance into an acid substance, and generating an ester substance from the acid substance and the alcohol substance, so that the hydroxyl value of the alcohol substance is reduced, and the VOC index of the recovered polyhydric alcohol is reduced; 3. the feeding device of the invention improves the feeding speed by about 3 times; meanwhile, in the same long reaction time, the dehydration time is prolonged, the water content of the recycled polyol is reduced, and the quality of the recycled polyol is obviously improved; because the feeding is accurate, the stable mass ratio of the pure PU foam feeding quality and the added main recycled alcoholysis agent is ensured, and the catalyst, the hexamethylenetetramine and the hydrogen peroxide can be timely added into a reaction system according to the process requirement, thereby ensuring the stability of each control index of each batch of recycled polyol; 4. the pure PU foam feeding mode is combined with the recovery process, and the recovered polyol with stable performance and relatively low water content and VOC (volatile organic compound) indexes can be produced; 5. the pure PU foam is quick to recover and feed, the efficiency is improved, and the cost is reduced.
The specific implementation mode is as follows:
for a better understanding and appreciation of the invention, specific embodiments thereof are described in detail below with reference to the accompanying drawings.
In the embodiment 1, referring to fig. 1, 2 and 3, according to design requirements, a weighing bin 9 and a screw conveyor 10 with proper specifications are selected, and are conventional devices and are connected; connecting a screw conveyor 10 with a feeding funnel 6 through a flexible connection 7, installing an auxiliary feeding double-helix feeding conveyor 5 at the lower end of the feeding funnel 6, wherein the auxiliary feeding double-helix feeding conveyor 5 operates more slowly than the screw conveyor 10; connecting an auxiliary feeding double-helix feeding conveyor 5 with a main feeding screw conveyor 4, connecting the main feeding screw conveyor 4 with a feeding reducing elbow 3, wherein the diameter of the interface of the main feeding screw conveyor 4 and the feeding reducing elbow 3 is phi 200, polishing the inner wall of the feeding reducing elbow 3, spraying a Teflon coating layer, and the surface energy of the inner wall is lower than 20 dyn/cm; communicating and connecting a feeding reducing elbow 3 with a reaction kettle 1 through a pneumatic gate valve 2, reducing the interface of the feeding reducing elbow 3 and the pneumatic gate valve 2 into phi 300, connecting the pneumatic gate valve 2 with the reaction kettle 1 through a flange, and self-lubricating and sealing a movable valve core and a fixed valve shell of the pneumatic gate valve 2 through a polytetrafluoroethylene sealing gasket; a small material feeding device 8 is arranged on the reaction kettle 1, and the small material feeding device 8 consists of a feeding funnel, a valve and a pipeline; the special recovery and feeding device for the alcoholysis of the industrial pure PU foam is formed.
By adopting the special recycling and feeding device of the embodiment 1, the alcoholysis recycling method comprises the following process steps:
a, introducing dry nitrogen to exhaust air in a reaction kettle 1, adding a main alcoholysis agent and a catalyst into the reaction kettle 1, wherein the addition amount of the catalyst accounts for 0.1-0.12% of the total mass of the recovered polyol; pure PU foam crushed aggregates (with the diameter of about 30 mm) to be recycled are weighed by a weighing bin 9, and then are conveyed into a feeding hopper 6 connected with a flexible connector 7 by a screw conveyor 10; the main alcoholysis agent is one or the mixture of two or more of ethylene glycol, 1, 4-butanediol, diethylene glycol, dipropylene glycol and polyethylene glycol 400; the catalyst is prepared from t-12 and triethylene diamine;
b, relatively rotating and extruding pure PU foam crushed aggregates temporarily stored in a loose state in a feeding hopper 6 by an auxiliary feeding double-spiral feeding conveyor 5 which operates later than the screw conveyor 10 into the main feeding screw conveyor 4 through a plurality of rows of spirally arranged feeding teeth (the tooth space and the top end are both larger than 30mm, and the tooth end with the tooth length of 100mm has radian to prevent the pure PU foam crushed aggregates from being hung upside down);
c, the main feeding screw conveyor 4 pushes the extruded pure PU foam crushed aggregates into the feeding reducing elbow 3 to push the resistance of the pure PU foam in the reducing elbow 3 to be gradually reduced (the resistance is gradually reduced due to the gradually increased inner diameter of the elbow, so that the PU foam crushed aggregates can enter the reaction kettle) to rapidly enter the feeding hole of the pneumatic gate valve 2 which is opened at the same time;
d, rapidly feeding the pure PU foam crushed aggregates into the reaction kettle 1 through a feeding hole on a movable valve core of the pneumatic gate valve 2 to finish the feeding process of the pure PU foam crushed aggregates at one time; pure PU foam crushed aggregates are added in a plurality of times, and hexamethylene tetramine is correspondingly added in a plurality of times through a small material feeding device 8 of a reaction kettle, wherein the total adding amount of the hexamethylene tetramine accounts for 0.13-0.15% of the total mass of the recycled polyol; after the feeding is finished each time, the movable valve core of the pneumatic gate valve 2 is quickly reset, the part of the movable valve core without the feeding hole is communicated with the reaction kettle 1 and is sealed, and the polyol steam in the reaction kettle 1 is prevented from overflowing;
e, the mass ratio of the addition amount of the pure PU foam crushed aggregates to the addition amount of the main alcoholysis agent is 46-48: 54-52; carrying out recovery reaction at 160-190 ℃ until all pure PU foam in the reaction kettle 1 is completely alcoholyzed; and f, after alcoholysis is completed, cooling the inside of the reaction kettle to 70-75 ℃, adding hydrogen peroxide (with the hydrogen peroxide content of 30%) into the reaction kettle at one time from the bottom of a small material feeding device 8 of the reaction kettle, wherein the adding amount of the hydrogen peroxide is 0.40-0.43% of the total mass of the recovered polyol, continuously stirring for reaction for 1 hour, completely reacting aldehyde substances in the recovered polyol, heating the reaction kettle to 115-125 ℃, controlling the outlet temperature of a condensation reflux device and a moisture separation device to be 105-110 ℃, continuously stirring by a stirrer of the reaction kettle, removing the generated moisture for 1 hour under the drive of dry nitrogen until the moisture content of the recovered polyol is detected to be below 0.1%, cooling to 80-90 ℃, filtering by a 60-mesh stainless steel filter screen, and discharging to finish the primary polyol recovery production process.
The above-described embodiments are intended to be illustrative only and not to limit the scope of the invention, and various changes or modifications may be made therein by those skilled in the art after learning the content of the present invention, which equivalents are also within the scope of the invention as defined in the appended claims.