Method of manufacturing PVC and PVC products

Abstract

The present invention relates to a method for producing a vinyl chloride-containing copolymer by emulsion polymerization, and in particular provides a method for producing a vinyl chloride-containing copolymer, comprising the steps of: a. batch copolymerizing a mixture containing a vinyl chloride monomer (A) and a comonomer (B) in an emulsion polymerization process, i. the weight ratio of A:B added to the polymerization process is higher than 10:1, such that the corresponding copolymer contains less than 10% by weight of comonomer, and ii. the comonomer (B) is added 1. continuously for at least 50% of the reaction time, or 2. in multiple additions, with the interval between the first and last addition being at least 50% of the reaction time, or 3. a combination of the above, and b. after the reaction time, i. increasing the temperature of the reaction mixture, ii. removing unreacted vinyl chloride for at least 10 minutes, and c. recovering the vinyl chloride-containing copolymer. The present invention also provides a vinyl chloride-n-butyl acrylate copolymer, the use of said copolymer in a PVC product, and a PVC product containing the vinyl chloride-n-butyl acrylate copolymer.

Description

[Technical field]

[0001] The present invention relates to a process for the preparation of vinyl chloride-containing copolymers by emulsion polymerization. [Background technology]

[0002] Polyvinyl chloride (PVC) is one of the most important thermoplastic materials on the market today, due to its very good mechanical and physical properties which make it suitable for many applications. Several processes are known for the preparation of PVC. For example, PVC can be prepared by suspension polymerization of vinyl chloride in a suspension and in the presence of a suspending agent. This produces a slurry (or suspension) of PVC particles, usually with particle sizes on the order of 30-200 μm. The resulting PVC slurry is then dried, usually by centrifugation followed by fluidized bed drying, to give porous (i.e. adsorbent) PVC. PVC produced by the suspension process is referred to as "S-PVC". S-PVC can be imbibed with a thermoplasticizer to give a dried formulation. PVC can also be produced by what are known as the paste or emulsion polymerization process. The emulsion polymerization process may be characterized in that the polymerization produces a latex of polymer particles that are relatively small in size than the S-PVC process, typically between 0.01 and 5 μm. The latex may be dried, for example by spray drying, to produce PVC granules in the form of agglomerates. The dried PVC polymer granules are usually much smaller than the dried particles produced by the suspension PVC process. It is known to add additives to PVC to make it suitable for various applications. It is also known to polymerize vinyl chloride monomer in the presence of comonomers that impart improved properties. The most typical comonomer for PVC is vinyl acetate. Other specific types of comonomers that find application in PVC are alkyl acrylates or methacrylates.

[0003] International Patent Application No. 2014 / 188971 describes, for example, a vinyl chloride-containing copolymer prepared by copolymerizing 30 to 98% by weight (inclusive) of an acrylic copolymer with 2 to 70% by weight (inclusive) of a vinyl chloride monomer, the acrylic copolymer being prepared by copolymerizing 100 parts by weight of an alkyl (meth)acrylate monomer with 0.1 to 10 parts by weight (inclusive) of a polyfunctional monomer. WO 2015 / 090657 describes, for example, a method for the preparation of a copolymer of a halogenated vinyl monomer and at least one other monomer B, where the monomer B is a monomer whose Tg is lower than the Tg of the polymer formed by polymerizing the at least one halogenated vinyl monomer. The method comprises a series of process steps in which each monomer is introduced in different amounts into the polymerization process. The addition of alkyl acrylates can provide polymers with improved properties in terms of lower gel temperature, i.e., lower gel temperature, which is advantageous for many applications, but this may come at the expense of other advantageous or desirable properties, particularly viscosity. Summary of the Invention

[0004] The present invention relates to copolymers with a comonomer of vinyl chloride, said comonomer being present at relatively low levels in the final product. It is an object of the present invention to provide a PVC copolymer having an improved combination of properties, in particular a relatively low gelling temperature. In particular, the inventors of the present invention have discovered that improved vinyl chloride-containing copolymers can be obtained by polymerizing vinyl chloride with a comonomer in an emulsion polymerization process with specific control of the in-process introduction of the comonomer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Thus, in a first aspect, the present invention provides a method for producing a vinyl chloride-containing copolymer, comprising the steps of: a. batch copolymerizing a mixture comprising vinyl chloride monomer (A) and comonomer (B) in an emulsion polymerization process, i. the mass ratio of A:B added to said polymerization process is greater than 10:1, such that the corresponding copolymer contains less than 10% by weight of comonomer; ii. The comonomer (B) is 1. Continuously for at least 50% of the reaction time, or 2. By multiple separate additions with an interval between the first and last addition of at least 50% of the reaction time; or 3. Combination of the above The step of adding b. After a reaction time, i. increasing the temperature of the reaction mixture; ii. stripping off unreacted vinyl chloride for at least 10 minutes; c. recovering the vinyl chloride-containing copolymer; The present invention provides a method comprising:

[0006] The present invention relates to an emulsion polymerization process. The term "emulsion polymerization" as used herein adopts the IUPAC definition "a polymerization in which monomers, initiator, dispersion medium, and optionally colloidal stabilizers are initially organized in a heterogeneous system, resulting in particles of colloidal dimensions containing the formed polymer." According to the above definition, and as used herein, emulsion polymerization includes "miniemulsion" and "microsuspension" polymerization processes, both as defined by IUPAC. In some embodiments, the polymerization may be a "seeded polymerization," in which pre-prepared polymer particles ("seeds") are added to the process and polymerization is carried out in situ to form larger particles. This may, for example, allow for the preparation of larger particles than can be obtained from a single-step polymerization process, and / or the production of bimodal particles with improved properties, such as mechanical stability. The copolymer comprises a vinyl chloride monomer (A) and a comonomer (B). The comonomer (B) is preferably a comonomer that reduces the glass transition temperature of the copolymer compared to the PVC homopolymer. In particular, the glass transition temperature, Tg, of the vinyl chloride-containing copolymer is preferably less than 82° C. Such comonomers are known in the art and are in fact commonly referred to as “soft monomers” because they reduce the glass transition temperature. Particularly preferred comonomers for the embodiment, and therefore for the comonomer (B) of the process of the present invention, include vinyl carboxylates, vinyl ethers, olefins and alkyl (meth)acrylates. Particularly preferred comonomers (B) are vinyl carboxylates, especially vinyl acetate, and alkyl (meth)acrylates.

[0007] Additional comonomers, either additional "soft monomers" of the type described above, or other comonomers, may be present during polymerization. However, all embodiments of the first aspect of the invention require that the corresponding copolymers contain less than 10% by weight of comonomer. Thus, when multiple comonomers are present, the total amount of comonomers in the resulting copolymer must still be less than 10% by weight. In a preferred embodiment, the comonomer (B) is an alkyl (meth)acrylate. The term "alkyl (meth)acrylate" is used herein in a contraction to refer to alkyl acrylate and alkyl methacrylate. For example, butyl (meth)acrylate refers to butyl methacrylate and butyl acrylate. In a preferred embodiment, the comonomer (B) is an alkyl acrylate. However, as described below, it should be understood that even when the embodiments of the invention refer only to acrylates, they can be equally applied to the equivalent methacrylates and even to any other comonomers, unless the context clearly indicates otherwise.

[0008] Preferred alkyl (meth)acrylates include C1-C10 alkyl groups. Preferred alkyl groups include C2-C8 alkyl groups. Particularly preferred alkyl (meth)acrylates according to the invention are alkyl acrylates rather than alkyl methacrylates. Particularly preferred alkyl acrylates for use as comonomers according to the invention are ethyl acrylate, ethylhexyl acrylate, t-butyl acrylate and n-butyl acrylate, with n-butyl acrylate being most preferred. A particular feature of the first aspect of the present invention is that the vinyl chloride-containing copolymer produced contains less than 10% by weight of comonomer. The term "copolymer" as used herein includes not only products having a single comonomer (e.g., vinyl chloride and n-butyl acrylate), but also products having two or more comonomers (e.g., vinyl chloride and n-butyl acrylate and an additional comonomer). Products containing vinyl chloride and two comonomers may also be referred to as, for example, terpolymers, which are included within the definition of copolymer as used herein. If only one comonomer, e.g., n-butyl acrylate, is present, this means that the copolymer contains less than 10% by weight (based on the total of the monomers) of this comonomer. If additional comonomers are present, this means less than 10% by weight of the sum of all comonomers.

[0009] In general, the comonomer content of the product can be measured by any suitable method. One suitable method, and preferred for purposes of the present invention, is: 1 The use of H nuclear magnetic resonance (NMR) spectroscopy. Preferably, the copolymer comprises at least 1% by weight of comonomer, such as at least 2% by weight of comonomer, most preferably at least 3% by weight of comonomer. Preferably, the copolymer comprises less than 9% by weight of comonomer, such as less than 8% by weight of comonomer, more preferably less than 7% by weight of comonomer. In a preferred embodiment where the comonomer (B) is an alkyl(meth)acrylate, the copolymer preferably comprises at least 1% by weight of alkyl(meth)acrylate, such as at least 2% by weight of alkyl(meth)acrylate, most preferably at least 3% by weight of alkyl(meth)acrylate. Preferably, the copolymer comprises less than 9% by weight of alkyl(meth)acrylate, such as less than 8% by weight of alkyl(meth)acrylate, more preferably less than 7% by weight of alkyl(meth)acrylate. In an embodiment, the copolymer may preferably contain 3 to 7 weight percent alkyl (meth)acrylate.

[0010] In other embodiments, particularly where the copolymer is produced by microsuspension polymerization, the copolymer may preferably contain 4-8 wt.% alkyl (meth)acrylate, which has been found to produce polymers with low gelling temperatures and low viscosities. The alkyl (meth)acrylate content ranges apply when the alkyl (meth)acrylate is the only comonomer or when another comonomer is present (and when more than one alkyl (meth)acrylate is present, the ranges apply to the total alkyl (meth)acrylates present). When comonomer (B) is an alkyl (meth)acrylate, typical additional comonomers, if present, may include a second alkyl (meth)acrylate or another suitable comonomer. Examples of other comonomers that can be used include (meth)acrylic acid, maleic anhydride, vinyl acetate, other monomers containing carboxylate groups (e.g., diallyl phthalate, allyl methacrylate, and diallyl maleate, discussed below), acrylamide and derivatives, vinylidene chloride, and allyl and vinyl ethers.

[0011] In some preferred embodiments, there may be two alkyl (meth)acrylates in the polymerization, particularly two alkyl acrylates. For example, the polymerization may include a mixture of vinyl chloride monomer (A) and at least two alkyl (meth)acrylate comonomers, preferably two alkyl acrylate comonomers. A particularly preferred combination involves the use of both n-butyl acrylate and ethylhexyl acrylate as comonomers. In all embodiments in which one or more additional comonomers are present in addition to comonomer (B), particularly preferred classes of additional comonomers that may be present include crosslinking or chain extending monomers. Such monomers are known in the art as comonomers for use with vinyl chloride. Preferred examples include diallyl phthalate, allyl methacrylate, diallyl maleate, trimethylolpropane diallyl ether, and triethylene glycol divinyl ether or diethylene glycol divinyl ether, among others. The weight ratio of A:B added to the polymerization process is greater than 10:1, such that the corresponding copolymer contains less than 10% by weight comonomer. For the avoidance of doubt, this "weight ratio" refers to the total amount of A relative to the total amount of B added during the polymerization, regardless of when it is added.

[0012] An essential feature of the present invention is that the comonomer (B) is added at different times throughout the polymerization. 1. Continuously for at least 50% of the reaction time, or 2. By multiple separate additions with an interval between the first and last addition of at least 50% of the reaction time; or 3. Combination of the above is added. In the context of using alkyl (meth)acrylates as comonomers, for example, alkyl (meth)acrylates tend to react faster than vinyl chloride. The same is true for many of the other comonomers suitable for use as comonomer (B). For at least this reason, but also because comonomer (B) is present in the final copolymer only at relatively low levels in all embodiments, adding it in multiple stages ensures that the composition of the copolymer is more uniform throughout the polymerization process, resulting in a more uniform product structure. Without being bound by theory, it is believed that this, too, is related to the improved properties obtained.

[0013] (The product obtained by this invention is believed to have the comonomer more evenly distributed throughout the bulk of the polymer particle due to the requirement of when the comonomer is added. This can be contrasted with the product obtained when the comonomer is present initially but not added "later" in the polymerization, where most of the comonomer is found in the core of the particle, or with the product obtained when the comonomer is not added initially but only at a later stage of the polymerization, where said comonomer is found in the outer layers of the product.) As used herein, "reaction time" is the total time measured from the start of polymerization until either (i) a step is taken to stop the reaction and / or (ii) the reaction pressure drops due to the release of vinyl chloride. In particular, in a typical batch emulsion polymerization process, a stirred, temperature-controlled, pressure-resistant reaction vessel, also called an autoclave, is charged with the monomer, the dispersion medium (usually water) and the stabilizer. It is important to remove oxygen (as it is a radical scavenger) from the autoclave and the reaction medium. Vinyl chloride monomer is immiscible in water and takes the form of vinyl chloride droplets dispersed in the reaction medium and also exists as a gas phase above the emulsion. The polymerization reaction temperature is usually in the range of 40-80°C, especially 45-55°C (the reaction is exothermic and the temperature is controlled by removing the heat of reaction at the rate at which it is produced). Pressure can rise due to the vapor pressure of vinyl chloride.

[0014] Typically, the process is allowed to react for several hours, e.g., 4-8 hours, during which time the conversion of vinyl chloride monomer and other comonomers increases. The reaction pressure is usually fairly uniform for most of the reaction, but there may be small fluctuations in pressure, typically "spikes," as monomers or other components are added during the process. At some stage, vinyl chloride monomer begins to evolve in the liquid phase and the amount of vinyl chloride in the gas phase becomes insufficient to maintain the saturation vapor pressure. This is observed in the reaction profile as a steady decrease in reactor pressure. In accordance with the present invention, this pressure drop, as commonly used in the art, marks the end of the "reaction time" (unless the reaction is stopped earlier, e.g., by the addition of a terminating or "killer" agent). Typical reaction times may depend on the process conditions but may be known to those skilled in the art from previous experience with those particular systems / conditions. Typically, reaction times are between 4 and 8 hours. It should be noted that additional copolymerization (of vinyl chloride and comonomer) can continue after this time, particularly during step (b) of the present invention as described below, however, any such subsequent time is not part of the "reaction time" for purposes of the present invention.

[0015] In a first option of the present invention, which is preferred, the comonomer is added continuously for at least 50% of the reaction time. For the avoidance of doubt, the addition according to this requirement can be stopped or temporarily interrupted, so long as it is added continuously for at least 50% of the total reaction time. For example, in a 4 hour reaction time, comonomer (B) can be added continuously for the first 60 minutes of the reaction time, stopped for 15 minutes, then added continuously for the next 60 minutes, stopped for another 15 minutes, and then added continuously for another 60 minutes before stopping for the final 30 minutes (before a pressure drop is observed). The total time of continuous addition in this example is 3 hours, which is 75% of the 4 hour reaction time. Most preferably, comonomer (B) is added continuously to the process for at least 75% of the reaction time.

[0016] In a second option of the present invention, the comonomer (B) is added multiple times with an interval between the first and last addition of at least 50% of the reaction time. It is preferred that the interval between the first and last addition is at least 75% of the reaction time. In this option, the comonomer may be added in at least two portions, preferably at least three portions, more preferably at least four portions. Each addition may involve a single (i.e. "one-off" or "instant") injection, or may involve an addition over an extended period of time, for example 5-10 minutes or more. (When this is the case for either or both of the first and last additions, the first and last additions with an interval between them of a certain percentage of the reaction time refer to the start of the first addition and / or the end of the last addition.) In a preferred embodiment, the addition of comonomer (B) is started within 1 hour after the start of the reaction time and / or up to 25% of the reaction time has elapsed. (Regarding the option to start adding comonomer (B) before 25% of the reaction time has elapsed, it should be noted that this requirement (i) comonomer (B) is added continuously to the process for at least 75% of the reaction time; and (ii) Comonomer (B) is added in multiple increments with an interval between the first and last addition of at least 75% of the reaction time. The aim is to essentially satisfy the following:

[0017] In absolute terms, it is preferred that the addition of comonomer (B) commence within 30 minutes after the start of the reaction time (ie early in the reaction), more preferably within 10 minutes after the start of the reaction time. Additionally or alternatively, it is preferred that the addition of comonomer (B) is started within 10% of the reaction time, more preferably within 5% of the reaction time. Most preferably, comonomer B is present early in the reaction (whether added continuously or by initial addition). When comonomer (B) is added in multiple additions, it is preferred to add it in discrete additions that can be dispersed relatively evenly throughout the reaction time. For example, in a process with a 4 hour reaction time and 4 additions, additions can be made at the beginning of the reaction and at approximately the 1 hour, 2 hour, and 3 hour time points. In the third option, a combination of option 1 and option 2 can be used. For example, one option falling under option 2 is to add the comonomer in multiple additions where the one or more additions are consecutive. If the sum of the one or more consecutive additions is greater than 50% of the total reaction time, both option 1 and option 2 can be satisfied.

[0018] In all options, it is preferred that neither comonomer (B), nor preferably any other monomer, is added during the final 15 minutes of the reaction time, particularly during this time that the reaction consumes any comonomer (B) remaining in the reaction medium. In relation to vinyl chloride, it can also be added continuously or in portions during the polymerization process. However, usually, preferably, the majority of the vinyl chloride added, preferably at least 70% of the vinyl chloride, is present at the beginning of the reaction. As an example, 80% of the total amount of vinyl chloride may be present at the beginning of the reaction, with two additions of about 10% of the total amount each being carried out during the reaction time. The above additions relate to the addition of comonomer (B) and vinyl chloride. If additional comonomers are added, they can be added in any suitable manner / over any suitable time scale. Any additional comonomers may, for example, be added singly or in large part at the beginning of the reaction (including before the start) in a similar manner to the vinyl chloride monomer. Alternatively, they can be added continuously or in several portions spaced apart throughout the reaction time in a similar manner to comonomer (B).

[0019] The method of the present invention further comprises the steps of: i. increasing the temperature of the reaction mixture; ii. removing unreacted vinyl chloride for a period of at least 10 minutes; The method includes step (b). Step (b) is carried out after a "reaction time". In particular, it is contemplated that step (b) of the present invention is initiated immediately after the end of the reaction time (i.e., the end of the reaction time constitutes the start of step (b)), although it is not critical that step (i) or step (ii) themselves be initiated immediately after the start of step (b). Typically, and highly preferably, no monomer is added to the reaction mixture during step (b). In step (i), the temperature of the reaction mixture is increased. Typically, this can be achieved by reducing the cooling applied and using heat from the remaining polymerization to heat the process. However, additional heating can be applied if desired. The temperature may be increased by at least 10° C., such as at least 20° C., above the temperature at the end of the reaction period. Typically, in this step, the temperature may be increased to a temperature of 70-85° C., preferably to a temperature of 75-80° C. This can be compared with normal polymerization temperatures of 40-70° C., especially 45-55° C.

[0020] The temperature is typically increased over a period of at least 10 minutes, for example from 15 minutes to 1 hour. The increase in temperature acts to increase the conversion of the unreacted monomers, especially vinyl chloride. Typically, the conversion after this step is greater than 90% for vinyl chloride monomer. In step (ii), any unreacted vinyl chloride is stripped from the mixture over a period of at least 10 minutes. This step is usually carried out after step (i) and in a preferred embodiment of the invention may be accomplished by releasing any residual pressure in the reactor and venting the contents while maintaining an elevated temperature, particularly the temperature of step (ii), which results in the evaporation and removal of unreacted vinyl chloride from the emulsion. In this step, a vacuum may be applied to aid in the stripping, particularly to reach the boiling point of the continuous medium (water). The discharged components can be collected for reuse. However, in other embodiments, the reactor contents can be removed from the reactor and transferred to a separate vessel for the stripping step, in which case the external stripping process can be either batch or continuous. The removing step is preferably carried out for at least 20 minutes, for example, from 20 minutes to 1 hour.

[0021] In a preferred embodiment, step (b) further comprises adding an alkali metal hydroxide to the polymerization reaction medium, with sodium hydroxide being most preferred. The alkali metal hydroxide can be added at the start of step (b), for example just after the end of the reaction period, or the increase in temperature in step (i) can be initiated first and the alkali metal hydroxide or other compound added during the temperature increase, or even at the end of the temperature increase. (In other embodiments, the alkali metal hydroxide can be added at any time after step (b), such as before venting or removing from the reactor.) Step (b) typically takes a total of 30 minutes to 2 hours. It is generally desirable to minimize the time of step (b) so that additional batch reactions can be carried out quickly, but this must be balanced with the desire to remove residual monomer. The removed vinyl chloride copolymer is then recovered from the process. Typically, the product is recovered from the reactor as a latex of the copolymer and dried, for example by spray drying, as in the prior art. The latex can also be dried by using any available technique known in the art for drying latex (including coagulation). The final product, after drying, typically contains less than 1 ppm vinyl chloride monomer and less than 100 ppm comonomer.

[0022] More generally, the present invention provides a method for producing a vinyl chloride-containing copolymer, which is a batch copolymerization in an emulsion polymerization process. The above processes are known and some of the usual details have already been described. In general, apart from the requirements of the present invention and those described above, particularly those related to the addition of comonomers during the reaction, the polymerization process can be operated according to any of the above known batch emulsion polymerization process conditions, including, for example, any type of reactor suitable for such polymerization. Also, as already mentioned, the above conditions can include "conventional" emulsion polymerization process conditions, which are more commonly referred to as "mini-emulsion" and "microsuspension" polymerization processes, both of which are known in the art. The polymerization can, for example, be with initiators, stabilizers, buffers and other ingredients that are typically added to the above reactions. Examples of suitable conditions and ingredients can be found, for example, in International Patent Application No. 2013092730, International Patent Application No. 2015090657 and European Patent Application Publication No. 2960271.

[0023] As already mentioned, a particularly preferred comonomer (B) for the process of the first aspect of the present invention is n-butyl acrylate. In a second aspect, there is provided a vinyl chloride-n-butyl acrylate copolymer, preferably produced according to the process of the first aspect of the invention. In this second aspect, preferred copolymers are those preferred as for the copolymers of the first aspect, for example in terms of comonomer content, further comonomers which may be present. For example, the copolymer preferably comprises less than 10% by weight of n-butyl acrylate, preferably less than 9% by weight of n-butyl acrylate, such as less than 8% by weight of n-butyl acrylate, more preferably less than 7% by weight of n-butyl acrylate. Preferably, the copolymer comprises at least 1% by weight of n-butyl acrylate, such as at least 2% by weight of n-butyl acrylate, most preferably at least 3% by weight of n-butyl acrylate, such as at least 4% by weight of n-butyl acrylate. In embodiments, the copolymer may preferably contain 3-7 wt.% n-butyl acrylate. In other embodiments, particularly when the copolymer is produced by microsuspension polymerization, the copolymer may preferably contain 4-8 wt.% n-butyl acrylate. This range has been found to produce polymers with low gelling temperatures and low viscosities.

[0024] In a first embodiment of this second aspect of the invention, the vinyl chloride-n-butyl acrylate copolymer is A) 23℃ 1.4s according to ISO3219 and ISO / TC61 / N4710 -1 The plastisol rheology measured at is 24 Pa s or less, B) the gelling temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 76°C or less; The plastisol rheology and gel temperature listed above are measured on a plastisol formed by mixing the copolymer with 55 percent diisononyl phthalate, a vinyl chloride-n-butyl acrylate copolymer. In particular, the copolymers of this embodiment exhibit a favorable combination of low plastisol rheology and low gelation temperature. They may also exhibit low Tg (glass transition temperature) and good thermal stability. This embodiment particularly relates to copolymers produced by microsuspension polymerization processes, where both low gelation temperature and low plastisol rheology are desirable. (It should be noted that microsuspension and emulsion grades of vinyl chloride copolymers usually have different properties and are usually used for different applications. This embodiment relates to microsuspension grades (plastisol rheology) due to the viscosity requirements, while emulsion grades may have a viscosity higher than 24 Pa·s under the measurement method described in this embodiment (55 phr diisononyl phthalate).)

[0025] It is known that the addition of n-butyl acrylate can reduce the gel temperature compared to the corresponding vinyl chloride homopolymer. However, the addition of n-butyl acrylate can also increase the plastisol rheology, which is undesirable. It has been found that the addition of n-butyl acrylate according to the method of the present invention reduces the gel temperature even more than the addition of n-butyl acrylate at the beginning of the polymerization, but the increase in plastisol rheology is less than that of the homopolymer, and in some cases even decreases it. In this first embodiment, the copolymer may comprise at least 3% but less than 15% by weight of n-butyl acrylate, such as at least 3% but less than 10% by weight of n-butyl acrylate. Preferably, in this first embodiment, the copolymer may comprise 4-8% by weight of n-butyl acrylate.

[0026] Preferably, in this first embodiment, the temperature is 23° C. 1.4 s according to ISO 3219 and ISO / TC 61 / N 4710. -1 In some embodiments, the plastisol rheology measured at 23° C. 1.4 s in accordance with ISO 3219 and ISO / TC61 / N4710 is 23 Pa s or less, such as 22 Pa s or less, or 21 Pa s or less. -1 The plastisol rheology, measured at σ is 20 Pa·s or less, such as 15 Pa·s or less, or even 10 Pa·s or less. Typically the plastisol rheology is at least 2, such as at least 3 Pa·s. Preferably, the gelation temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 75° C. or less, such as 74° C. or less or 73° C. or less. In some embodiments, the gelation temperature is 72° C. or less, such as 70° C. or less, such as 65° C. or less or 60° C. or less. Typically, the gelation temperature is at least 50° C. (For the avoidance of doubt, all of the above are still measured on plastisol formed by blending the copolymer with 55 percent diisononyl phthalate, as previously defined.)

[0027] As may be known to those skilled in the art, plastisol rheology should be measured immediately after mixing with the plasticizer to minimize the effect of aging on the results. In the present invention, the rheology is measured within 1 hour after mixing the copolymer with diisononyl phthalate. Preferably, the gel temperature is also measured within 1 hour after mixing the copolymer with isononyl phthalate. In a second embodiment of this second aspect of the invention, the vinyl chloride-n-butyl acrylate copolymer is A) 23℃ 1.4s according to ISO3219 and ISO / TC61 / N4710 -1 The plastisol rheology measured at is 20 Pa s or more, B) the gelling temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 76°C or less; The plastisol rheology and gel temperature are measured on a plastisol formed by mixing the copolymer with 100 percent diisononyl phthalate, a vinyl chloride-n-butyl acrylate copolymer.

[0028] In particular, the copolymers of this embodiment exhibit a favorable combination of high plastisol rheology and low gel temperature. This embodiment is particularly directed to copolymers made by emulsion polymerization processes, where both low gel temperature and high plastisol rheology are desirable. (It is noteworthy that the high viscosity PVC resins are made by emulsion copolymerization rather than microsuspension, and therefore the above measurements are made with higher levels of plasticizer than the equivalent measurements with the microsuspension grades of the first embodiment, as is customary in the art. Despite the higher plasticizer levels, the plastisol rheology values ​​are higher than those of the first embodiment.) As in the case of microsuspension grades, it is known in emulsion grades that the addition of n-butyl acrylate can reduce the gel temperature compared to the corresponding vinyl chloride homopolymer. However, the addition of n-butyl acrylate at the beginning of polymerization when making emulsion grades can cause a significant decrease in plastisol rheology, which is undesirable in such grades. The addition of n-butyl acrylate according to the method of the present invention still desirably reduces the gel temperature, but it has been found that the plastisol rheology does not decrease significantly when the gel temperature is particularly decreased. This allows for copolymers with comparable gel temperatures and high plastisol rheology (alternatively, the addition of n-butyl acrylate can be adjusted to optimize the balance between gel temperature and plastisol rheology).

[0029] In this second embodiment, the copolymer may comprise at least 3% but less than 15% by weight of n-butyl acrylate, such as at least 3% but less than 10% by weight of n-butyl acrylate. Preferably, in this second embodiment, the copolymer comprises at least 4% by weight of n-butyl acrylate, such as 4-8% by weight of n-butyl acrylate. Preferably, in this second embodiment, the temperature is 23° C. 1.4 s according to ISO 3219 and ISO / TC 61 / N 4710. -1 The plastisol rheology measured at 23°C 1.4s according to ISO 3219 and ISO / TC 61 / N 4710 is 25 Pa s or more, such as 30 Pa s or more, 40 Pa s or more, or even 50 Pa s or more. -1 The plastisol rheology measured at is typically 140 Pa·s or less, for example 100 Pa·s or less. Preferably, the gelation temperature of this second embodiment, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 75° C. or less, such as 74° C. or less or 73° C. or less. In some embodiments, the gelation temperature is 72° C. or less. Typically, the gelation temperature is at least 50° C. More preferably, the gelation temperature is at least 64° C., such as at least 68° C.

[0030] (For the avoidance of doubt, as previously defined, any of the above are still measured on the plastisol formed by mixing the copolymer with 100 percent diisononyl phthalate, and as previously described for the first embodiment, the rheology, and preferably the gel temperature, are measured within one hour after mixing the copolymer with diisononyl phthalate.) The copolymer of the second embodiment may be formed of primary particles having a size distribution with a peak at or below 1.5 μm in size, with a half-width less than 50% of the particle size of the peak, as is typical for emulsion grades. Typically, the peak of the size distribution may be at or below 1 μm in size, such as at or below 0.5 μm, at or below 0.4 μm, or even at or below 0.2 μm. Typically, the peak of the size distribution may be at or above 0.01 μm, such as at or above 0.05 μm. (In contrast, the copolymers according to the first embodiment / microsuspension copolymers may have a particle size distribution peak at a size of up to 5 μm. They usually have a particle size distribution with a broad peak, i.e., a half-width that is more than 50% of the particle size of the peak.) The copolymer of the second embodiment has also been found to have improved gloss. In particular, the copolymer of this second embodiment may have a gloss of at least 75 GU (gloss units) measured according to ISO 2813. Preferably, the gloss is at least 80 GU. In some embodiments, the gloss may be at least 85 GU. Typically, the gloss may be up to 97 GU.

[0031] In a preferred embodiment, which applies to both the first and second embodiments above, the copolymer may have a glass transition temperature (Tg) of 80° C. or less, such as 79° C. or less or 78° C. or less, as measured by differential scanning calorimetry (DSC). In some embodiments, the Tg is 75° C. or less. Typically, the Tg is at least 64° C., such as at least 68° C., and most preferably at least 70° C. Their combination of properties makes the copolymers produced according to the first aspect of the invention or the copolymers according to the second aspect of the invention particularly useful in many common PVC applications, including use as flooring materials such as floor finishes and tiles, automotive underbody coatings, adhesives and sealants, and artificial leather materials. Thus, in a third aspect there is provided the use of a vinyl chloride-n-butyl acrylate copolymer produced according to the method of the first aspect, and / or a vinyl chloride-n-butyl acrylate copolymer of the second aspect, as a flooring material, an automotive underbody coating, an adhesive and sealant, or an artificial leather material.

[0032] In a fourth aspect, there is provided a PVC product comprising a vinyl chloride-n-butyl acrylate copolymer produced according to the method of the first aspect, and / or a PVC product which is a vinyl chloride-n-butyl acrylate copolymer of the second aspect, wherein the PVC product is a flooring material, an automotive underbody coating, an adhesive and sealant, or an artificial leather material. In preferred embodiments of these third and fourth aspects, the copolymer according to the first embodiment of the second aspect of the invention may be used as / part of a flooring material. In another preferred embodiment of these third and fourth aspects, the copolymer according to the second embodiment of the second aspect of the invention may be used as / part of an automotive underbody coating material. The invention can be illustrated by the following examples. EXAMPLES

[0033] Measurement method The following methods are used in the present examples. Unless otherwise specified, the values ​​of said parameters, if corresponding parameters are in the claims or throughout the specification of the present invention, are the values ​​that can be measured using these methods. The primary particle size distribution of the polymer latex was measured by photosedimentation analysis using an instrument manufactured by CPS Instruments Inc. The results are expressed as the apex size of each peak (μm) and the percentage of each peak (%). The results were obtained on a Brucker 500MHz instrument using deuterated chloroform (CDCl3) or deuterated tetrahydrofuran (THF-d8) as the solvent. 1 The percentage of monomer and the percentage of acrylate in the polymer were calculated from the 1 H nuclear magnetic resonance (NMR) spectrum. The thermal stability was evaluated using the procedure described in ISO 182-3, based on the detection of evolved hydrogen chloride and any acidic products at 180 °C. The equipment used was a 763 PVC Thermomat from Metrohm. The measurements were carried out on 0.5 g of PVC resin. The nitrogen flow rate was 7 L / h. The thermal stability time (expressed in minutes) is defined as the time required for the dehydrochlorination reaction at a temperature of 180 °C to reach an electrical conductivity of 50 μS / cm in a measuring cell containing ultrapure water. Glass transition temperatures were measured by differential scanning calorimetry (DSC). The equipment used was a Perkin Elmer Pyris 1 with a constant nitrogen flow rate of 30 mL / min. Samples (20 mg) were stabilized at -5°C for 5 min, then heated to 170°C at 20°C / min, cooled to -5°C at 20°C / min, held at -5°C for 15 min, and then heated to 170°C at 20°C / min. During this second heating, the glass transition was measured according to the standard method. Within 1 hour after mixing with either 55 phr or 100 phr of DINP (diisononyl phthalate) to form a plastisol, and within 1.4 to 1000 s at 23 °C in accordance with ISO 3219 and ISO / TC 61 / N 4710 -1 Plastisol rheology was measured using a Haake Rheostress 1 rotational rheometer between 0.05 ml / min (55 phr was used in Comparative Examples AC and Examples 1-6, and 100 phr was used in Comparative Examples D and E, and Examples 7-8). The gelation curves of the plastisols were obtained using an ARES rotational rheometer from TA instruments. The experiment consisted of an oscillatory temperature ramp at a constant angular frequency of 1 rad / sec from 25 to 150 °C at 3 °C / min. The resulting curve shows the complex viscosity versus temperature. The value reported as the gelation index is the temperature at which the viscosity reaches 10,000 Pa·s. The gloss of PVC films was measured according to ISO 2813. The gloss was measured on the side of the film not in contact with the release paper substrate. The instrument used was a Dr Lange REFO 3 with a matt black plate under a transparent film, calibrated to LZM 151 (gloss at 60° is 94.5GU).

[0034] Comparative Examples A to C and Examples 1 to 6 These examples describe polymerization under microsuspension conditions. (Comparative example A) In this example, vinyl chloride is polymerized under microsuspension conditions in the absence of comonomer. Specifically, 2.7 kg of water, 79.9 g of a 298 g / kg aqueous solution of sodium dodecylbenzenesulfonate, 4.15 g of dilauroyl peroxide (99.4%), 5.2 g of dimyristyl peroxydicarbonate (95.4%), 8.9 g of dioctyl adipate (100%), and 0.03 g of butylated hydroxyanisole (100%) were added to a 15 L premixer autoclave equipped with a stirrer and a double jacket, and mixed at 50 rpm. In a 15 L polymerization reactor also equipped with a stirrer and a double jacket, 2.7 kg of water, 1.8 g of sodium carbonate (100%), 119.9 g of a 298 g / kg aqueous solution of sodium dodecylbenzenesulfonate, and 645.8 g of a 384.1 g / kg aqueous solution of small PVC seeds having a size of 130 nm were added and mixed at 50 rpm.

[0035] Both reactors were connected and closed to the atmosphere, cycles of vacuum followed by nitrogen purge were applied, and finally vacuum was applied and the agitation speeds of the premixer autoclave and polymerization reactor were increased to 250 rpm and 110 rpm, respectively, after which 1985 g and 2977 g of vinyl chloride were charged to the premixer autoclave and polymerization reactor, respectively. A stirring step of 30 minutes was maintained to ensure mixing of all raw materials, after which the stirring speed of the premixer autoclave was reduced to 50 rpm and the premixer was connected to a two-stage high-pressure homogenizer previously placed under vacuum and recirculated for 5 minutes at two pressure stages of 120 bar and 40 bar before the mixture was transferred to the polymerization autoclave. Then, to rinse the premixer autoclave and ensure all reagents were transferred, 1 L of water was added to the premixer autoclave, stirred for 3 minutes, and transferred to the polymerization autoclave. Immediately after completing the transfer from the premixer autoclave, the reactor temperature was increased to reach the polymerization temperature (Tpol) of 49° C. Once Tpol was reached, this was defined as the start of polymerization (t0).

[0036] During the polymerization, two additional injections of 496 g vinyl chloride were introduced into the autoclave at t0+2h00 and t0+3h00. The reaction is allowed to proceed until a pressure drop is detected (-1 bar). In this particular comparative example, the time at which pressure drop was observed / reaction time was 7 hours 48 minutes. (It is worth noting that under these conditions, the time at which pressure drop is typically observed / reaction time is greater than 7 hours, typically between 7 and about 8 hours. This was typical for examples carried out under the microsuspension conditions of the present invention, although reaction times slightly longer than 8 hours were observed in several examples where n-butyl acrylate was added continuously. Without being bound by theory, this is believed to be due to the presence of small amounts of polymerization inhibitors added to the n-butyl acrylate to maintain storage stability, but which may slow the reaction rate when in use. However, in all of the examples 1-6 reported below, the reaction times were greater than 7 hours and n-butyl acrylate was added for 75% of the reaction time.) After a pressure drop was detected, the temperature of the polymerization medium was increased to 80° C. It was then possible to drain and remove the residual vinyl chloride from the autoclave (by injection of 3.0 g of a commercial antifoam agent). After the removal step (25 min), the autoclave was cooled to room temperature and flushed.

[0037] The solids concentration (or latex density) and pH of the latex were measured. The latex was filtered through a sieve with a mesh size of 1 mm. The latex was dried in a spray dryer and the resin obtained was sieved and ground according to the standard procedure. For the spray dryer, the inlet temperature is 160° C. and the outlet temperature is 60° C. The resin obtained was then ground in a Kolloplex 160Z (pin mill) at maximum intensity (14000 rpm). The resulting latex had a pH of 9.1, a solids concentration of 48%, and consisted of particles of 0.75 μm (87.3%) and 0.17 μm (12.7%). The thermal stability of the resin is 28.2 min. Plastisol rheology eta 1.4 showed 7.62 Pa·s. The gelation curve showed that the viscosity reached 10 kPa·s at 84.3°C, while DSC showed a Tg of 85.9°C.

[0038] (Comparative example B) Additionally, the procedure of Comparative Example A was repeated, except that 300.7 g of n-butyl acrylate was added to the premixer at the beginning of the process (during the first step, prior to connection to the polymerization reactor). (Vinyl chloride was continued to be added in a stepwise manner as described in Comparative Example A.) The resulting latex had a pH of 8.9, a solids concentration of 46.6%, and consisted of particles of 0.71 μm (88.5%) and 0.16 μm (11.5%). The n-butyl acrylate content of the resin was 3.8% by mass. The thermal stability of the resin is 16.8 min. The plastisol rheology eta of 1.4 was 24.5 Pa·s. The gelation curve showed that the viscosity reached 10 kPa·s at 76°C, while the DSC showed a Tg of 79.6°C.

[0039] Example 1 The procedure of Comparative Example B was repeated, except that 300.7 g of n-butyl acrylate was introduced continuously into the polymerization reactor between t0 and t0+7h00, instead of being introduced into the premixer. The resulting latex had a pH of 8.4 and a solids concentration of 46.4%, consisting of particles of 0.70 μm (88.1%) and 0.16 (11.9%). The thermal stability of the resin is 22.2 min. Plastisol rheology eta 1.4 showed 14.6 Pa·s. The gelation curve showed that the viscosity reached 10 kPa·s at 71°C, while DSC showed a Tg of 77.9°C. These examples show that the addition of n-butyl acrylate, either in a premixer (Comparative Example B) or continuously (Example 1) (as shown both by the reduction in the temperature required to reach a viscosity of 10 kPa·s and by the reduction in Tg), leads to a product with a lower gelling temperature compared to PVC homopolymer. However, this comes at the expense of an increase in viscosity. However, the comparison of Example 1 shows that the continuous addition of n-butyl acrylate according to the present invention results in an improved (lower) gel temperature and lower viscosity compared to the initial addition at or before the start of polymerization.

[0040] (Comparative example C) i) 330.8 g of n-butyl acrylate was added to the premixer at the beginning of the process (during the first step, before connecting with the polymerization reactor); ii) no PVC seeds were added to the polymerization reactor; and iii) The procedure of Comparative Example B was repeated except that a different homogenizer was used. Specifically, the procedure of Comparative Example B was repeated except that a colloid mill homogenizer was used and operated to recirculate the mixture five times at maximum speed. The reaction time was slightly shorter than expected in this Comparative Example C, about 6.5 hours (although, as noted above, it was over 7 hours as expected in Examples 2-6 below). Without being bound by theory, it is believed that consumption of the inhibitor and reaction of the n-butyl acrylate may have occurred during the heating time to reach the polymerization temperature prior to t0 in this Comparative Example. The resulting latex had a pH of 9, a solids concentration of 49.8%, and was composed of particles of 1.50 μm. The n-butyl acrylate content of the resin was 4.3% by mass. The plastisol rheology eta of 1.4 was 16.2 Pa·s. The gelation curve showed that the viscosity reached 10 kPa·s at 77.4°C.

[0041] Example 2 The procedure of Comparative Example C was repeated, except that 330.8 g of n-butyl acrylate was introduced continuously into the polymerization reactor between t0 and t0+7h00, instead of being introduced into the premixer. The resulting latex had a pH of 8.6, a solids concentration of 46.2%, and was composed of particles of 1.57 μm. The plastisol rheology eta 1.4 showed 4.7 Pa·s. The gelation curve showed that the viscosity reached 10 kPa·s at 71 °C, while DSC showed a Tg of 75.1 °C. Comparison with Comparative Example C of Example 2 shows that the continuous addition of n-butyl acrylate according to the invention also results in an improved (reduced) gel temperature and also a lower viscosity (eta 1.4) compared to addition at or before the initial polymerization initiation.

[0042] (Examples 3 to 6) The procedure of Example 2 was repeated, except that the amount of n-butyl acrylate (which was added continuously between t0 and t0+7h00 in each case) was increased. The effect on viscosity is shown below. [Table 1] These examples show that increasing the n-butyl acrylate content further reduces the gel temperature and Tg. The results also continue to show a low viscosity (eta 1.4) following the procedure according to the invention, but the viscosity increases again as the n-butyl acrylate content is increased. Comparative Examples D and E, and Examples 7 and 8 These examples demonstrate polymerization under emulsion conditions.

[0043] (Comparative example D) In this example, vinyl chloride is polymerized under emulsion conditions in the absence of comonomer. The polymerization was carried out in a 25 L polymerization reactor equipped with a stirrer and a double jacket. 11.99 kg of water, 28.4 mL of 2 g / L copper sulfate pentahydrate solution, and 79.3 g of 110 g / L myristic acid solution (NaOH / NH4OH ratio) were added to the reactor, which was then closed and the agitator speed set to 50 rpm. Air in the reactor was purged by cycles of vacuum and nitrogen purge before finally applying vacuum. The agitator speed was increased to 160 rpm and 7.9 kg of vinyl chloride was charged. Using a double jacket, the temperature was increased to reach the polymerization temperature (Tpol) of 52°C. Once Tpol was reached, polymerization was initiated by introducing 45.1 mL of 223 g / L ammonia, followed 5 minutes later by 42.6 mL of 100 g / L ammonium persulfate, which constitutes t0 of this example. At t0+0h20, a continuous feed of 110 g / L myristic acid solution (the same as that used at the start) was started. After starting it was added continuously until t0+2h45, corresponding to a total amount of 1257.9 g myristic acid solution. It was then stopped, after which the continuous introduction of 48 g / kg sodium lauryl sulfate solution was started and added until t0+4h00. The total amount of sodium lauryl sulfate solution added was 1056.3 g. In addition, two injections, each of 789 g vinyl chloride, were injected at t0+1h30 and t0+2h30.

[0044] Once a pressure drop was detected (approximately 1 bar), 75.8 mL of 40 g / L sodium hydroxide solution was added and the reactor temperature was increased to 80°C. A pressure drop was observed / reaction time was over 4 hours, which is normal for reactions under these conditions. The reactor was purged of unreacted vinyl chloride (by injection of 4.7 g of a commercial antifoam agent) and stripped (after addition of 2.5 mL of 223 g / L ammonia solution) over a period of 25 minutes. After the stripping step, the reactor was cooled to room temperature and 417 mL of 50 g / kg sodium carbonate solution was added. The latex was drained and the reactor was washed. The solids concentration and pH of the latex were 40.8% and 10.5, respectively. The latex was filtered through a sieve with a mesh size of 1 mm. The latex was dried in a spray dryer and the resulting resin was sieved and ground according to standard procedures. For the spray dryer, the inlet temperature was 160°C and the outlet temperature was 70°C. DSC showed a Tg of 79.9° C. and the resin had a gloss of 69 GU. The plastisol rheology eta of 1.4 was 92 Pa·s, while the gel temperature was 79°C.

[0045] (Comparative Example E) Additionally, the process of Comparative Example D was repeated, except that 489.2 g of n-butyl acrylate was added along with the initial amount of vinyl chloride at the beginning of the process (the vinyl chloride continued to be added in a stepwise manner as described in Comparative Example D). The reaction time was 4 hours. The solids concentration and pH of the latex were 36.2% and 12.3, respectively. The latex was filtered, dried and ground as in Comparative Example D. The n-butyl acrylate content of the resin was 4.6% by mass. DSC showed a Tg of 75.9° C. and the resin had a gloss of 85 GU. The gelation temperature was 64 °C, but the plastisol rheology eta of 1.4 was only 6.7 Pa·s.

[0046] Example 7 The procedure of Comparative Example D was repeated, except that 295.5 g of n-butyl acrylate was continuously introduced into the polymerization reactor between t0+0h30 and t0+4h00 (i.e., during the introduction of the first myristic acid solution first and then the introduction of the aqueous lauryl sulfate solution). The reaction time was 4 hours 35 minutes. The solids concentration and pH of the latex were 40.9% and 10.4, respectively. The n-butyl acrylate content of the resin was 3.8% by mass. DSC showed a Tg of 72.1° C. and the resin had a gloss of 89 GU. The gelation temperature was 67°C, and the plastisol rheology eta was 1.4 and 20 Pa·s. Therefore, a comparable gel temperature is obtained, albeit at a much higher plastisol rheology, compared to Comparative Example D. Also, a lower Tg is obtained.

[0047] Example 8 The procedure of Example 7 was repeated, except that 492.9 g of n-butyl acrylate was continuously introduced into the polymerization reactor between t0+0h30 and t0+4h00. The reaction time was 5 hours 19 minutes. The solids concentration and pH of the latex were 39.0% and 10.3, respectively. The n-butyl acrylate content of the resin was 4.9% by mass. DSC showed a Tg of 70.5° C. and the resin had a gloss of 92 GU. The gelation temperature was 63°C, and the plastisol rheology eta of 1.4 was 52 Pa·s. Thus, in comparison to Comparative Example D, the method of the present invention again results in a comparable gel temperature, albeit at a much higher plastisol rheology. Also, a lower Tg is obtained.

[0048] (Comparative example F) This comparative example is an addition example provided to illustrate the effect of adding n-butyl acrylate only at the latter stages of the polymerization. The polymerizations were carried out under microsuspension conditions. Specifically, 1.5 kg of water, 112.3 g of a 199.7 g / kg aqueous solution of sodium dodecylbenzenesulfonate, 3.9 g of dilauroyl peroxide, 5.88 g of dimyristyl peroxydicarbonate, 8.4 g of dioctyl adipate, and 0.03 g of butylated hydroxyanisole were added to a 15 L premixer autoclave equipped with a stirrer and a double jacket, and mixed at 50 rpm. In a 15 L polymerization reactor equipped with a stirrer and a double jacket, 3.5 kg of water, 1.7 g of sodium carbonate, 168.4 g of a 199.7 g / kg aqueous solution of sodium dodecylbenzenesulfonate, and 572.7 g of an aqueous dispersion of 407.8 g / kg fine PVC seeds were added and mixed at 50 rpm.

[0049] Both reactors were connected and closed to the atmosphere, cycles of vacuum followed by nitrogen purge were applied, and finally vacuum was applied and the agitation speeds of the premixer autoclave and polymerization reactor were increased to 250 rpm and 110 rpm, respectively, after which 2043.5 g and 3065.2 g of vinyl chloride were charged to the premixer autoclave and polymerization reactor, respectively. A stirring step of 30 minutes was maintained to ensure mixing of all raw materials, after which the stirring speed of the premixer autoclave was reduced to 50 rpm, the premixer was connected to a two-stage high-pressure homogenizer previously placed under vacuum, and the mixture was recirculated at two pressure stages of 120 bar and 40 bar for 5 minutes before being transferred to the polymerization autoclave. Then, to rinse the premixer autoclave and ensure all reagents were transferred, 1 L of water was added to the premixer autoclave, stirred for 3 minutes, and transferred to the polymerization autoclave.

[0050] Immediately after completing the transfer from the premixer autoclave, the polymerization autoclave temperature was increased thanks to the double jacket to reach a polymerization temperature (Tpol) of 49° C. Once Tpol was reached, this was defined as the start of polymerization (t0). From previous experiments under these conditions, it was estimated that 50% conversion of vinyl chloride occurred in about 5 hours. Thus, in this experiment, the addition of n-butyl acrylate was started 5 hours after the start. More specifically, 312.5 g of n-butyl acrylate (having a purity of 997.5 g / kg) was continuously introduced between t0+5h00 and t0+7h00. Two injections of 465 g of vinyl chloride were introduced into the autoclave at t0+2h00 and t0+3h00. After 8 hours, the temperature of the polymerization medium was increased to 80° C. It was then possible to drain and remove the residual vinyl chloride from the autoclave (by injection of 2.8 g of a commercial antifoam agent). After the removal step (25 min), the autoclave was cooled to room temperature and flushed. The solids concentration (or latex density) and pH of the latex were measured. The latex was filtered through a sieve with a mesh size of 1 mm. The latex was dried in a spray dryer and the resin obtained was sieved and ground according to the standard procedure. For the spray dryer, the inlet temperature is 160° C. and the outlet temperature is 60° C. The resin obtained was then ground in a Kolloplex 160Z (pin mill) at 14000 rpm.

[0051] The latex had a pH of 11.1, a mechanical stability of greater than 10 minutes, a solids concentration of 43.2%, and consisted of particles of 0.54 μm (75.2%) and 0.18 (24.8%). The thermal stability of the resin was 26.4 min and the eta of the 55 phr DINP plastisol rheology was 367 Pa·s. The gelation curve showed that the viscosity reached 10 kPa·s at 76.0°C, while the DSC showed a Tg of 82.6°C. The n-butyl acrylate content of the resin was 3.9% by mass. As can be seen above, the "post-addition" of n-butyl acrylate resulted in a product with a much higher viscosity (eta 1.4), and also an overall higher gel temperature and Tg (° C.).

Claims

1. A method for producing a vinyl chloride-containing copolymer, a. A mixture containing vinyl chloride monomer (A) and comonomer (B) is subjected to an emulsion polymerization process. A process of batch copolymerization using S, i. The mass ratio of A:B added to the polymerization process should be higher than 10:

1. The corresponding copolymer contains less than 10% by mass of comonomers. ii. Comonomer (B) is, 1. Continuously for at least 50% of the reaction time, or 2. The interval between the first and last additions is at least 50% of the reaction time. It is present, or by adding it multiple times, 3. With the above combinations The above step involves adding, b. After the reaction time, i. A step of raising the temperature of the reaction mixture, ii. A step of removing unreacted vinyl chloride for at least 10 minutes, c. A process for recovering vinyl chloride-containing copolymers and Methods that include...

2. The method according to claim 1, wherein the addition of comonomer (B) is started within one hour after the start of the reaction time and / or before 25% of the reaction time has elapsed.

3. The method according to claim 1, wherein the comonomer (B) is an alkyl (meth)acrylate.

4. The method according to claim 3, wherein the comonomer (B) is n-butyl acrylate.

5. The method according to claim 1, wherein the copolymer comprises 3 to 10% by mass of comonomer (B).

6. The method according to claim 1, wherein the comonomer (B) is continuously added to the process for at least 50% of the reaction time.

7. A) 23°C, 1.4 s in accordance with ISO 3219 and ISO / TC61 / N4710 -1 The plastisol rheology measured is 24 Pa·s or less. B) The gelation temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 76°C or lower. Vinyl chloride-n-butyl acrylate copolymer, The plastisol rheology and gelation temperature are measured using the plastisol formed by mixing the copolymer with 55 parts diisononyl phthalate per 100 parts copolymer. Vinyl chloride-n-butyl acrylate copolymer.

8. 23°C 1.4s according to ISO 3219 and ISO / TC61 / N4710 -1 The copolymer according to claim 7, wherein the plastisol rheology measured is 23 Pa·s or less, for example, 22 Pa·s or less, or 21 Pa·s or less.

9. The copolymer according to claim 7, wherein the gelation temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 74°C or lower, for example, 72°C or lower.

10. A) 23°C, 1.4 s in accordance with ISO 3219 and ISO / TC61 / N4710 -1 The plastisol rheology measured is 20 Pa·s or higher. B) The gelation temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 76°C or lower. Vinyl chloride-n-butyl acrylate copolymer, The plastisol rheology and gelation temperature are measured using the plastisol formed by mixing the copolymer with 100 parts diisononyl phthalate per 100 parts copolymer. Vinyl chloride-n-butyl acrylate copolymer.

11. 23°C 1.4s according to ISO 3219 and ISO / TC61 / N4710 -1 The copolymer according to claim 10, wherein the plastisol rheology measured is 25 Pa·s or more, for example, 30 Pa·s or more, 40 Pa·s or more, or even 50 Pa·s or more.

12. The copolymer according to claim 10, wherein the gelation temperature, measured as the temperature at which the viscosity reaches 10,000 Pa·s, is 74°C or lower, for example, 72°C or lower.

13. The copolymer according to claim 10, wherein the copolymer has a gloss of at least 75 GU (gloss units), preferably at least 80 GU, as measured according to ISO 2813.

14. The copolymer according to any one of claims 7 to 13, wherein the copolymer has a glass transition temperature (Tg) of 80°C or less, for example, 78°C or less, or 75°C or less, as measured by differential scanning calorimeter (DSC).

15. The copolymer according to any one of claims 7 to 13, wherein the copolymer comprises at least 3% by mass but less than 15% by mass of n-butyl acrylate.

16. The copolymer according to claim 15, wherein the copolymer contains at least 3% by mass but less than 10% by mass of n-butyl acrylate.

17. A composition comprising the vinyl chloride-n-butyl acrylate copolymer according to any one of claims 7 to 13, for use in flooring materials, underbody coating materials for automobiles, adhesives and sealants, or artificial leather materials.

18. A PVC product comprising a vinyl chloride-n-butyl acrylate copolymer manufactured according to the method of any one of claims 1 to 6, preferably the vinyl chloride-n-butyl acrylate copolymer according to any one of claims 7 to 13, which is a flooring material, an underbody coating for automobiles, an adhesive and sealant, or an artificial leather material.

19. A composition comprising the vinyl chloride-n-butyl acrylate copolymer according to claim 16 for use in flooring materials, underbody coating materials for automobiles, adhesives and sealants, or artificial leather materials.

20. A PVC product comprising the vinyl chloride-n-butyl acrylate copolymer described in Claim 16, wherein the PVC product is a flooring material, an underbody coating for automobiles, an adhesive and sealant, or an artificial leather material.