Method for producing ethylene-carboxylic acid copolymer

Abstract

To provide a method of producing ethylene-carboxylic acid copolymer which can suppress generation of a self-polymer in a discharging unit and reduce equipment failures thereby enhancing the copolymer yield.SOLUTION: In a method of producing an ethylene-carboxylic acid copolymer, a monomer solution containing a carboxylic acid monomer is supplied from a discharging unit. The carboxylic acid monomer is copolymerized with an ethylene-based monomer. A coefficient of friction between the discharging unit and the monomer solution in the discharging unit is maintained at 0.3 or less. Accordingly, generation of a self-polymer in the discharging unit can be suppressed and equipment failures are reduced thereby enhancing the copolymer yield.SELECTED DRAWING: Figure 1a

Description

[Technical field]

[0001] The present invention relates to a method for producing an ethylene-carboxylic acid copolymer, more particularly, to a method for producing an ethylene-carboxylic acid copolymer that includes pumping of a carboxylic acid monomer. [Background technology]

[0002] For example, ethylene-carboxylic acid copolymers such as ethylene-acrylic acid copolymers are used in a variety of applications, including sealing materials, adhesives, packing materials, and optical films.

[0003] The ethylene-carboxylic acid copolymer can be produced by polymerizing ethylene and a carboxylic acid compound (eg, acrylic acid, methacrylic acid, etc.) as a comonomer in a continuous reactor.

[0004] Carboxylic acid compounds have a higher self-reactivity than ethylene, and therefore may self-polymerize when exposed to high temperatures during the process of being supplied from a flow path, pump, compressor, etc. In this case, equipment defects such as clogging and blockage of the flow path of the pump, compressor, flow path, etc. may occur, which may reduce the production yield of the copolymer and make it difficult to uniformly repeat the process.

[0005] Therefore, a method of using an additive to suppress self-polymerization in addition to the monomer for polymerizing the copolymer has been studied. However, the additive may cause environmental pollution problems and may affect the yield of the copolymer. Therefore, it is necessary to consider how to suppress self-polymerization in the design of the polymerization apparatus.

[0006] For example, International Patent Publication WO2016 / 172076 discloses the use of a polymerization inhibitor to prevent fouling in a polymerization reaction, but does not disclose a design for preventing self-polymerization in the above-mentioned equipment or process units. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for producing an ethylene-carboxylic acid copolymer, which can achieve improved process reliability and polymerization efficiency. [Means for solving the problem]

[0008] In the method for producing an ethylene-carboxylic acid copolymer according to an exemplary embodiment of the present invention, a monomer solution containing a carboxylic acid monomer can be supplied from a discharge part. The carboxylic acid monomer can be copolymerized with an ethylene-based monomer. The friction coefficient between the discharge part and the monomer solution in the discharge part can be maintained at 0.3 or less.

[0009] In some embodiments, the coefficient of friction between the discharge portion and the monomer solution can be maintained at 0.1 or less.

[0010] In some embodiments, the discharge portion may include a piston and a packing portion that encases the piston.

[0011] In some embodiments, the coefficient of friction between the surface of the piston and the monomer solution and the coefficient of friction between the packing and the monomer solution can both be maintained at 0.3 or less.

[0012] In some embodiments, the piston and the packing part may each have a surface roughness (Ra) of less than 75 nm.

[0013] In some embodiments, the piston and the packing portion may each have a surface roughness (Ra) of 2 nm or less.

[0014] In some embodiments, the temperature within the outlet may be 85° C. or less.

[0015] In some embodiments, the temperature inside the discharge section may be 20 to 60°C.

[0016] In some embodiments, a lubricating composition may further be provided within the discharge portion.

[0017] In some embodiments, the dissolved oxygen in the lubricating composition may be 10 ppm or less.

[0018] In some embodiments, the lubricating composition may include a base oil and a phenothiazine-based polymerization inhibitor, and the content of the polymerization inhibitor in the lubricating composition may be 0.1 to 10 ppm.

[0019] In some embodiments, after the monomer solution is dispensed from the outlet, the ethylene-based monomer may be injected and copolymerized.

[0020] In some embodiments, the monomer solution may further include the ethylene-based monomer. The monomer solution including the carboxylic acid monomer and the ethylene-based monomer may be injected into a reactor from the outlet to be copolymerized. Effect of the Invention

[0021] According to an embodiment of the present invention, the friction coefficient of the discharge part that comes into contact with the carboxylic acid monomer can be adjusted to suppress the formation of self-polymerization, such as polyacrylic acid (PAA), thereby improving the yield of the desired copolymer and suppressing clogging of the polymerization apparatus.

[0022] In some embodiments, the coefficient of friction at which self-polymerization does not occur can be stably maintained by adjusting the surface roughness of the discharge section, the temperature / pressure within the discharge section, and the like. [Brief description of the drawings]

[0023] [Figure 1a]1 is a schematic process flow diagram illustrating a method for producing a copolymer according to an exemplary embodiment. [Figure 1b] 1 is a schematic process flow diagram illustrating a method for producing a copolymer according to an exemplary embodiment. [Diagram 2] 1 is a schematic cross-sectional view illustrating a discharge portion according to an exemplary embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing a disk and a ball of a friction force measuring device. [Figure 4] 1 is an actual image of the disk and ball of a friction force measuring device. [Diagram 5] 1 is a graph showing changes in friction coefficient in Experimental Example 1. [Figure 6] 1 is a graph showing changes in friction coefficient in Experimental Example 1. [Figure 7] 1 is a graph showing changes in friction coefficient in Experimental Example 1. [Figure 8] 13 is a graph showing changes in friction coefficient in Experimental Example 2. [Figure 9] 13 is a graph showing changes in friction coefficient in Experimental Example 2. [Figure 10] 13 is a graph showing changes in friction coefficient in Experimental Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] SUMMARY OF THE DISCLOSURE An embodiment of the present invention provides a method for producing an ethylene-carboxylic acid copolymer, which includes pumping a carboxylic acid monomer through a discharge portion, and is capable of preventing self-polymerization of the carboxylic acid monomer.

[0025] Hereinafter, the present invention will be described in more detail with reference to specific experimental examples and drawings. However, the drawings attached to this specification are intended to illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to aid in further understanding of the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited only to the matters depicted in the drawings.

[0026] 1a and 1b are schematic process flow charts for explaining a method for producing an ethylene-carboxylic acid copolymer according to an exemplary embodiment. FIG. 2 is a schematic cross-sectional view showing a discharge part according to an exemplary embodiment.

[0027] Referring to FIG. 1a, a first monomer supplying unit 10 can supply a first monomer solution including a carboxylic acid monomer.

[0028] The carboxylic acid monomer may include an unsaturated carboxylic acid capable of chain polymerization reaction. According to an exemplary embodiment, the carboxylic acid monomer may be (meth)acrylic acid or its ester (e.g., (meth)acrylate). In the present application, (meth)acrylic acid is used as a term that includes methacrylic acid and acrylic acid.

[0029] For example, a first monomer solution including a carboxylic acid monomer can be delivered to the discharge unit 30 from a first monomer supply unit 10 such as a storage tank through a first flow path 20 .

[0030] For example, one or more additives such as reaction inhibitors, antioxidants, etc. may be included in the first monomer solution.

[0031] The first monomer solution may travel to the discharge section 30 and be discharged via the discharge passage 40 for copolymerization with, for example, ethylene polymerizable monomers.

[0032] The discharge section 30 may include, for example, a discharge device such as a pump or a compressor.

[0033] 2, the discharge part 30 may include a piston 32 and a packing part 34. The carboxylic acid monomer supplied through the discharge passage 40 may be pumped or ejected by the reciprocating motion of the piston 32 inside the packing part 34. The packing part 34 may be a sealing member such as a bushing or a cylinder.

[0034] For example, the first monomer solution may be ejected by relative reciprocating and / or rotating motion of the piston 32 and the packing portion 34 .

[0035] 2, friction between the piston 32 and the packing part 34 occurs repeatedly in the gap between the piston 32 and the packing part 34, which may generate a friction generation region (FR). In the friction generation region (FR), localized temperature increases may occur due to frictional heat. This may result in the self-polymerization temperature of the carboxylic acid monomer being exceeded, or if the activation energy required for self-polymerization is satisfied by frictional energy, self-polymerization such as polyacrylic acid (PAA) may occur.

[0036] In this case, clogging of the gap occurs, shortening the replacement or cleaning period of the discharge part 30, reducing the process efficiency and the yield of the desired copolymer.

[0037] According to an exemplary embodiment, the coefficient of friction (CoF) between the first monomer solution and the discharge portion 30 can be adjusted to 0.3 or less. For example, the coefficient of friction between the first monomer solution and the piston 32 and the coefficient of friction between the first monomer solution and the packing portion 34 can both be adjusted to 0.3 or less.

[0038] This can substantially suppress the self-polymerization occurring in the friction generating region (FR). Preferably, the coefficient of friction (CoF) between the first monomer solution and the discharge portion 30 can be adjusted to 0.1 or less.

[0039] The friction coefficient between the first monomer solution and the discharge part 30 can be adjusted by the contact pressure in the discharge part 30, the pumping temperature, the rotational speed or translational speed of the piston 32 inside the packing part 34, the surface roughness of the piston 32 and / or the packing part 34, etc.

[0040] In some embodiments, the surface roughness (Ra) of the surface of the discharge part 30 that comes into contact with the first monomer solution may be less than 75 nm. Preferably, the surface roughness of the surface of the discharge part 30 that comes into contact with the first monomer solution may be 2 nm or less. In this range, an increase in frictional force can be suppressed even under harsh discharge conditions, and the generation of self-polymerization can be substantially prevented.

[0041] In some embodiments, the temperature (e.g., pumping temperature) in the discharge portion 30 may be up to 85° C. This temperature range can substantially reduce the possibility of self-polymerization of the carboxylic acid monomers.

[0042] Preferably, the temperature inside the discharge part 30 may be 20 to 60° C. Within this range, the friction coefficient inside the discharge part 30 is maintained constant without fluctuation or disturbance, and a stable discharge process can be continuously maintained.

[0043] In some embodiments, the contact pressure between the piston 32 and the packing portion 34 in the discharge portion 30 may be about 5,400 bar or more. This range facilitates maintaining a coefficient of friction at the discharge portion 30 of 0.3 or less. In one preferred embodiment, the contact pressure between the piston 32 and the packing portion 34 may be about 8,100 bar or more.

[0044] In some embodiments, a lubricating composition can be provided in the discharge portion 30 along with the first monomer solution. The lubricating composition includes a mineral oil and can further include a self-polymerization inhibitor, such as a phenothiazine-based compound.

[0045] Phenothiazine compounds can cause environmental problems, and therefore, when contained in a lubricating composition, the phenothiazine compounds may be contained in an amount of 20 ppm or less, preferably in the range of 0.1 to 10 ppm.

[0046] Even if a small amount of a phenothiazine-based compound is contained as described above, or even if no phenothiazine-based compound is contained, the generation of self-polymerization (e.g., PAA) can be sufficiently suppressed by adjusting the friction coefficient in the discharge portion 30 described above.

[0047] In one embodiment, the dissolved oxygen in the lubricating composition can be adjusted to 10 ppm or less. When the dissolved oxygen is in this range, it is possible to prevent, for example, the promotion of radical self-polymerization caused by the active oxygen contained in the lubricating composition.

[0048] The second monomer solution stored in the second monomer supply unit 50 may move through the second flow path 55 to contact the carboxylic acid-based monomer supplied from the discharge flow path 40 and be copolymerized in the reactor 60. According to an exemplary embodiment, the second monomer solution may include an ethylene-based polymerizable monomer.

[0049] When ethylene is used as the second monomer, copolymerization of a carboxylic acid monomer with ethylene can be carried out in reactor 60 to produce an ethylene-carboxylic acid copolymer (e.g., an EAA copolymer).

[0050] In some embodiments, a polymerization initiator may be co-introduced into the reactor 60 via the second flow path 55 or another flow path, to prevent the polymerization initiator from prematurely promoting the self-polymerization of the carboxylic acid monomer.

[0051] For example, the polymerization initiator may be any initiator known in the field of polymer polymerization, such as a peroxide or peroxy compound, or an azobis compound.

[0052] In some embodiments, a chain transfer agent can be introduced during the polymerization process, for example, via second flow path 55. The chain transfer agent can facilitate control of the molecular weight and molecular weight distribution of the polymer product to a desired range.

[0053] Chain transfer agents can include, for example, non-polar organic compounds such as isobutane, propyne, or polar organic compounds such as methyl ethyl ketone, isopropyl aldehyde, vinyl acetate, and the like.

[0054] The temperature in the reactor 60 may be higher than the temperature in the discharge section 30. For example, the temperature in the reactor 60 may be about 150 to 270°C.

[0055] In some embodiments, the pressure in reactor 60 may range from 1,100 to 2,500 bar, preferably from 1,300 to 2,300 bar. In one embodiment, the pumping pressure in discharge section 30 may be greater than the copolymerization pressure in reactor 60. For example, the pumping pressure in discharge section 30 may range from 1,500 to 3,000 bar.

[0056] 1b, a first monomer supply unit 10 and a second monomer supply unit 50 may supply monomer solutions and mix them together. Thus, a mixed monomer solution including a carboxylic acid monomer and an ethylene monomer may be supplied to a discharge unit 30 through a first flow path 20.

[0057] The mixed monomer solution may be pumped from the discharge part 30 and supplied to the reactor 60 through the discharge passage 40. For example, the mixed monomer solution may react with a polymerization initiator injected into the reactor 60 to obtain an ethylene-carboxylic acid copolymer.

[0058] 1b, when the mixed monomer solution is supplied into the discharge part 30, for example, an EAA copolymer may be pre-formed, which may cause clogging of the discharge part 30. In this case, too, as described above, the coefficient of friction between the discharge part 30 and the mixed monomer solution may be adjusted to reduce or prevent fouling caused by the EAA copolymer and a decrease in process efficiency.

[0059] Specific experimental examples are presented below to aid in understanding the present invention, but the examples and comparative examples included in these experimental examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It is clear to those skilled in the art that various changes and modifications can be made to these examples within the scope of the scope and technical ideas of the present invention, and it is natural that these changes and modifications fall within the scope of the appended claims.

[0060] Experimental Example 1 A monomer solution was prepared by mixing 20% ​​by weight of acrylic acid (AA) (purity 99%, Sigma-Aldrich) with base oil (HYPERCOMP-1000, manufactured by SK Innovation). The friction coefficient of the prepared monomer solution was measured by rotating a disk and ball using a friction force measuring device (Mini-Traction Machine (MTM) 2) to observe whether self-polymerization occurred.

[0061] Figure 3 is a schematic diagram showing the disk and ball of the friction force measuring device, and Figure 4 is an actual image of the disk and ball of the friction force measuring device.

[0062] 3 and 4, a monomer solution at an initial temperature of 55° C. was supplied into the disk 72 through an inlet 76 coupled with the ball 74, and then the disk 72 and the ball 74 were rotated together to come into contact with the monomer solution.

[0063] The coefficient of friction (CoF) was measured while changing the load between the disk 72 and the ball 74, and the slide roll ratio (SRR) between the ball 74 and the disk 72. In addition, the presence or absence of self-polymerization was also observed.

[0064] The load between the disk 72 and the ball 74 can substantially correspond to the contact pressure between the piston 32 and the packing portion 34 in the discharge portion 30. A load of 37 N corresponds to a contact pressure of 1 GPa (approximately 10,000 bar), and for example, a load of 20 N can correspond to approximately 5,400 bar.

[0065] Specifically, the possibility of friction may increase as SRR increases. When SRR is 0%, the ball 74 and the disk 72 may rotate in the same direction and at the same speed. When SRR is 100%, for example, the ball 74 may rotate alone while the disk 72 is stationary. When SRR is 200%, the ball 74 and the disk 72 may rotate in opposite directions and at the same speed.

[0066] On the other hand, repeated experiments were carried out using two disks, one with a surface roughness of 2 nm (hereinafter referred to as the "polished disk") and the other with a surface roughness of 75 nm (hereinafter referred to as the "rough disk"). The rotational speed of the ball 74 and / or disk 72 was adjusted to 250 mm / s.

[0067] 5 to 7 are graphs showing changes in the friction coefficient in Experimental Example 1. In FIG.

[0068] Specifically, in Figures 5 to 7, Sample 1 is an example where a base oil (excluding AA) and an abrasive disc were used, Sample 2 is an example where a monomer solution and an abrasive disc were used, Sample 3 is an example where a base oil and a rough disc were used, and Sample 4 is an example where a monomer solution and a rough disc were used.

[0069] The samples of Example 1 commonly had coefficients of friction greater than 0.3 and precipitation of PAA self-polymer was observed at the bottom of the disk 72 .

[0070] As shown in Figure 5, compared to sample 3, which contained only base oil with a rough disk, the friction coefficient of sample 4, which contained AA, increased sharply and exceeded 0.3 over virtually the entire SRR range. Also, in the cases of samples 1 and 2, which used polished disks, the friction coefficient was stably maintained at less than 0.1, where no self-polymerization occurred.

[0071] Referring to Fig. 6, as the pumping load increased to 30 N, the rate of increase in the friction coefficient in Sample 4 slowed down. Referring to Fig. 7, as the pumping load increased to 50 N, the friction coefficient was suppressed to less than 0.3 when the SRR was 10%.

[0072] Experimental Example 2 The lubricant used was CL1000 lube oil (manufactured by Sonneborn), and the same rough disk, base oil, AA monomer and monomer solution were used as in Experimental Example 1. The increase in friction coefficient due to SRR was observed while changing the temperature and load.

[0073] 8 to 10 are graphs showing changes in the friction coefficient in Experimental Example 2.

[0074] Specifically, sample 5 is an example where a base oil (excluding AA) was used with a load of 20N, sample 6 is an example where a monomer solution was used with a load of 20N, sample 7 is an example where a base oil (excluding AA) was used with a load of 30N, sample 8 is an example where a monomer solution was used with a load of 30N, sample 9 is an example where a base oil (excluding AA) was used with a load of 50N, and sample 10 is an example where a monomer solution was used with a load of 50N.

[0075] 8 and 9, in all samples, the friction coefficient was stably maintained below 0.1, at which self-polymerization is inhibited.

[0076] Referring to FIG. 10, as the temperature increased to 100° C., the friction coefficient increased in the sample containing AA, and an irregular increase and decrease was observed.

Claims

1. A method for producing an ethylene-carboxylic acid copolymer using an apparatus including a discharge section, comprising: supplying a monomer solution containing a carboxylic acid monomer from the discharge portion; copolymerizing the carboxylic acid monomer with ethylene monomer; The method for producing an ethylene-carboxylic acid copolymer, wherein a friction coefficient between the discharge part and the monomer solution in the discharge part is maintained at 0.3 or less.

2. 2. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein a friction coefficient between the discharge part and the monomer solution is maintained at 0.1 or less.

3. 2. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the discharge portion includes a piston and a packing portion that encases the piston.

4. The method for producing an ethylene-carboxylic acid copolymer according to claim 3, wherein a friction coefficient between the surface of the piston and the monomer solution and a friction coefficient between the packing part and the monomer solution are both maintained at 0.3 or less.

5. The method for producing an ethylene-carboxylic acid copolymer according to claim 3, wherein the piston and the packing part each have a surface roughness (Ra) of less than 75 nm.

6. The method for producing an ethylene-carboxylic acid copolymer according to claim 3, wherein the piston and the packing portion each have a surface roughness (Ra) of 2 nm or less.

7. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the temperature in the discharge section is 85° C. or lower.

8. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the temperature in the discharge section is 20 to 60°C.

9. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, further comprising supplying a lubricant composition into the discharge section.

10. The method for producing an ethylene-carboxylic acid copolymer according to claim 9, wherein the lubricating composition has a dissolved oxygen content of 10 ppm or less.

11. The method for producing an ethylene-carboxylic acid copolymer according to claim 9, wherein the lubricating composition contains a base oil and a phenothiazine-based polymerization inhibitor, and the content of the polymerization inhibitor in the lubricating composition is 0.1 to 10 ppm.

12. 2. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the step of copolymerizing the carboxylic acid monomer with the ethylene monomer comprises injecting the ethylene monomer after the monomer solution is supplied from the discharge portion.

13. The monomer solution further comprises the ethylene monomer, 2. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the step of copolymerizing the carboxylic acid monomer with the ethylene monomer comprises injecting the monomer solution containing the carboxylic acid monomer and the ethylene monomer from the discharge portion into a reactor.

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