CN110437591B

CN110437591B - High-viscosity PBT (polybutylene terephthalate) material for optical cable and preparation method thereof

Info

Publication number: CN110437591B
Application number: CN201910758361.5A
Authority: CN
Inventors: 胥保礼; 崔晓文; 姚君
Original assignee: Nantong Xingchen Synthetic Materials Co Ltd
Current assignee: Nantong Xingchen Synthetic Materials Co Ltd
Priority date: 2019-08-16
Filing date: 2019-08-16
Publication date: 2021-04-23
Anticipated expiration: 2039-08-16
Also published as: CN110437591A

Abstract

The invention discloses a high-viscosity PBT material for an optical cable and a preparation method thereof, wherein the PBT material is prepared by freezing a part of PBT resin and grinding the part of the PBT resin into powder for later use; and then premixing the obtained powder PBT with an auxiliary agent including a chain extender, adding the rest non-ground granular PBT, and performing heating melting, uniformly mixing reaction, air exhaust, vacuum exhaust, extrusion granulation to obtain the high-viscosity PBT material for the optical cable. The obtained PBT material has the intrinsic viscosity of more than 1.3dL/g and good viscosity stability, can effectively avoid the bulge phenomenon in a loose tube production line, and does not have adverse effects on the properties such as mechanical strength and the like. The method for preparing the PBT material provided by the invention has the advantages of easily obtained raw materials, simple process, no need of complex and expensive equipment, can be completed by a double-screw extruder, is an economic and efficient method for producing the high-viscosity PBT material for the optical cable, and is suitable for large-scale industrial production.

Description

High-viscosity PBT (polybutylene terephthalate) material for optical cable and preparation method thereof

Technical Field

The invention belongs to the field of polyester materials, and particularly relates to a high-viscosity PBT material for an optical cable and a preparation method thereof.

Background

At present, the 5G technology is rapidly developed, and as an infrastructure of the 5G era, the optical cable plays a key role in the development in the future. The requirements for loose optical cable tubes in the industry are also increasing, and a plurality of optical fibers which are arranged in parallel are generally arranged in the loose tube, so that the loose tube is required to be large in diameter, stable in pore size, and appropriate in rigidity and flexibility.

At present, the loose tube for optical cables and optical fibers is mainly made of PBT (polybutylene terephthalate), the PBT has high tensile strength and elongation at break, can keep stable in high-temperature and humid environments, and the excellent comprehensive performance of the PBT enables the PBT resin to be widely applied to various fields, particularly the loose tube for optical cables and optical fibers is the last layer of the optical cable in the manufacturing process of the optical cable, can protect the optical fibers from the influence of internal stress and external side pressure, and plays a role in coating and protecting the optical fibers. The PBT material for the optical cable is generally prepared by extrusion processing of high-viscosity PBT resin, and has high requirement on intrinsic viscosity (about 1.3 dL/g) and small change of viscosity.

The general-purpose PBT intrinsic viscosity is generally 0.7-1.1dL/g, and in order to obtain the high-viscosity PBT, the domestic main production mode is solid-phase tackifying, namely, the high-viscosity PBT resin with the intrinsic viscosity of 1.2-1.3dL/g is obtained by adding a proper additive into the medium-viscosity PBT resin with the intrinsic viscosity of 1.0-1.1dL/g, uniformly mixing, tackifying, cooling, dedusting, conveying to a storage bin, packaging, transporting and the like. Different additives are required to be added in the whole production process, and the production process can be divided into different specifications according to different additives. According to the existing production experience, most of the added additives are in a powder state, and a vacuum pump is easily blocked in the subsequent vacuum, so that equipment failure is caused. In order to solve the problem, patents CN104109352A and CN104109354A propose a method of preparing PBT functional master batch, and add the functional master batch and PBT resin into a solid phase adhesion increasing device according to a ratio of 1:10 to solve the problem of powder additive. However, the difficulty of this method is that 10% of the master batch is uniformly mixed in the PBT resin, and a common tackifying device cannot achieve uniform mixing. The mode is an intermittent method, the difference between batches is large, the energy consumption of the device is high, the yield is low, continuous production cannot be achieved, and in the application of downstream optical cable enterprises, the method cannot adapt to the pultrusion process of high-speed optical cables, and the defects of optical cable bulge, uneven pipe wall thickness, unstable pipe diameter, unsmooth surface and the like are easily caused.

Patent CN107602835A has proposed the mode of using the chemical chain extension, adopt the on-line tackification reaction of twin-screw extruder, reach the viscosity stability of serialization production and control product, just can add the various auxiliary agents that need into the system together at the beginning simultaneously, avoided making the masterbatch earlier and going on the process of tackification after the back mixes evenly, the process has been simplified, the production efficiency is improved, the equipment investment is few, convenient operation, the suitability is strong, advantages such as easy popularization have been obtained certain progress.

However, as the requirement of the optical cable production enterprise on the pultrusion speed of the optical cable is higher and higher, the requirement on the PBT material for the optical cable is also higher and higher, the method mentioned in the above patent also faces more and more challenges, and the prepared material cannot meet the more and more strict requirements of downstream customers, which is mainly reflected in the following points: (1) in the process of tackifying the PBT material, a plurality of auxiliary agents are required to be added, the auxiliary agents are all in powder form, the melting points of some auxiliary agents are lower, and the auxiliary agents can be melted at the opening part of a charging hopper, so that the charging accuracy is influenced, the prepared PBT optical cable material is not uniform, the thickness and the pipe diameter of the prepared optical cable loose tube are not uniform, and the swelling phenomenon easily occurs at part of places to cause complaints; (2) because the proportion of various additives is small, and the additives are uniformly mixed in the PBT resin in a granular form, the specific surface area of the PBT granules is small, the effect of uniform dispersion cannot be achieved by mixing, and the viscosity consistency of the tackifying particles cannot be achieved. The high-viscosity PBT resin produced by the method has the advantages of difficult control of viscosity, yellow color, unstable molecular chain and easy degradation, and is difficult to meet the quality requirement of the current optical cable industry on raw materials.

Aiming at the defects of the technology and the requirements of market customers on the refinement of materials, the invention provides a new solution and scheme to use the existing equipment and adjust the existing process conditions and steps to prepare the PBT material for optical cable bulk, which meets the market requirements, is stable, uniform and consistent in color.

Disclosure of Invention

The invention aims to solve the problems of the method and provide the PBT material for the optical cable, which has high quality, stable viscosity, highly controllable production process and smooth and bubble-free extrusion molding surface.

In order to achieve the purpose, the invention adopts the following technical scheme:

the high-viscosity PBT material for the optical cable comprises the following raw materials in parts by weight: 100 parts of PBT base resin and 0.5-3 parts of chain extender; is obtained by a preparation method comprising the following steps:

1) freezing a part of PBT resin, and grinding into powder for later use;

2) and premixing the powder PBT and an auxiliary agent including a chain extender, adding the rest unground PBT base resin, and performing heating melting, uniformly mixing reaction, air exhaust, vacuum exhaust, extrusion granulation to obtain the high-viscosity PBT material for the optical cable.

The freezing and grinding can be carried out by methods known in the art, such as a liquid nitrogen freezing and crushing machine, wherein the freezing temperature is-50 ℃ to-190 ℃, and the freezing time is 1-10 minutes; preferably, the freezing temperature is-90 ℃ to-130 ℃ and the freezing time is 1-3 minutes. And then sending the frozen PBT into a grinder, and achieving the effect of fully grinding through repeated impact grinding.

The intrinsic viscosity of the PBT base resin is 1.0-1.1dL/g, the PBT base resin is in a particle shape in an initial state, the particle size is adjusted by regulating and controlling the rotating speed and the grinding time of a grinding machine, and the PBT base resin is sieved after grinding to obtain PBT powder with D50 of 100-500 mu m, preferably PBT powder with D50 of 200-400 mu m.

The PBT resin subjected to freeze grinding accounts for 20-40 parts.

The inventor unexpectedly finds that the PBT material obtained by controlling the proportion of the powder PBT and the particle size D50 in the above range has good consistency, and the prepared optical cable loose tube has uniform thickness and tube diameter, thereby greatly improving the bulging phenomenon of the common PBT material. If the content of the PBT used for premixing is too small, the PBT cannot be effectively mixed with the additives such as the chain extender and the like, and the effect of good consistency of the PBT material cannot be achieved; too much PBT is used in the premix, which in turn may have an effect on the mechanical properties of the resulting PBT.

The chain extender is not particularly limited, and any chain extender conventionally used in polyester reaction in the art may be used, and a multipolymer of acrylate having a high reactive group, such as at least one of isocyanates, bisoxazoline and diepoxide compounds, is generally used. Examples of chain extenders that may be mentioned include, but are not limited to, diphenylmethane diisocyanate (MDI), 2, 4-Toluene Diisocyanate (TDI), 2, 6-toluene diisocyanate, isophorone diisocyanate (IPDI).

Optionally, the auxiliary agent further comprises 0.1-0.4 part of antioxidant, 0.5-2.0 parts of end capping agent and 0.3-0.8 part of lubricant. Preferably, the antioxidant is selected from at least one of pentaerythritol ester (antioxidant 1010), triphosphite (antioxidant 168) and dipentaerythritol diphosphite (antioxidant 626); and/or the lubricant is selected from at least one of pentaerythritol stearate (PETS) and polyethylene wax; the end-capping reagent is ethylenediamine.

The invention adopts a single-screw or double-screw extruder, preferably a double-screw extruder, wherein the screw of the air exhaust section adopts large-area shallow threads to fully overflow bubbles; the screw pitch of the large-area shallow thread screw is 56-112 mm; the vacuum degree of the vacuum exhaust section is 100-500Pa, preferably 100-300Pa, and low molecular substances and bubbles are further removed by vacuum exhaust.

The vacuum degree in the present invention is referred to as "absolute vacuum degree".

Due to the process of melt extrusion of the materials in the screw, a small amount of degradation can occur, and a small amount of low molecular substances are generated, so that bubbles are formed. If the bubbles can not be removed, the quality consistency and viscosity of the PBT material of the subsequent product can be adversely affected, and the PBT material with excellent comprehensive performance can not be obtained.

The invention also provides application of the PBT material to manufacturing a loose tube for an optical cable. The PBT material prepared by the invention is used as the loose tube for the optical cable, has excellent mechanical property and electrical property, and particularly has obviously reduced bulging times. The PBT material is a PBT material of the loose tube for the optical cable with excellent comprehensive performance.

Compared with the prior art, the invention has the following beneficial technical effects:

firstly, a part of PBT base resin is creatively frozen and ground into powder with the particle size of D50-.

Secondly, the high-viscosity PBT material for the optical cable provided by the invention can be produced by only adding a small amount of chain extender, so that the PBT material with the intrinsic viscosity of more than 1.3dL/g can be obtained, and the problem of unstable product quality caused by large using amount of the chain extender is effectively avoided due to the small adding amount of the chain extender.

And in the double-screw extrusion process, residual monomers and micromolecule volatile matters are fully discharged through the air exhaust process and the vacuum exhaust process, so that the consistency of the PBT material for optical cable and optical fiber loose tube products is facilitated.

The specific implementation mode is as follows:

the following examples are intended to illustrate the high viscosity PBT material for optical cables of the invention but should not be construed as limiting the scope of the invention. The examples do not show the specific techniques or conditions, according to the technical or conditions described in the literature in the field, or according to the product specifications. The reagents or instruments used are conventional products available from regular distributors, not indicated by the manufacturer.

In the examples, the terms "parts" and "parts" are used in parts by mass unless otherwise specified, and the terms "degree of vacuum" and "degree of vacuum" are used herein in the same way.

Example 1

Step 1: weighing 100 parts of PBT base resin, wherein the intrinsic viscosity of the PBT base resin is 1.02dL/g, freezing 20 parts of the PBT base resin by using liquid nitrogen according to a certain proportion at-130 ℃ for 3min, and grinding the resin in a frozen state into powder PBT by using a grinder, wherein the particle size D50 is about 400 mu m;

step 2: uniformly mixing the powder PBT with 1.2 parts of chain extender MDI, 0.2 part of antioxidant AT10, 0.2 part of antioxidant 168 and 0.3 part of lubricant PETS;

and step 3: conveying the mixture obtained in the step 2 to a feed opening of a double-screw extruder through a pipeline, and feeding the mixture and the rest 80 parts of PBT particles into the feed opening of the double-screw extruder;

and 4, step 4: adding 1.0 part of end capping agent hexamethylene diamine before an air exhaust section of a double-screw extruder to terminate the reaction; the large-area shallow threads are used for fully overflowing air bubbles in the air exhaust section of the double-screw extruder; the low molecules and bubbles were removed again in the vacuum degassing section of the twin-screw extruder with a high vacuum of 100 Pa.

And 5: and cooling, granulating, drying and packaging the extruded material strips according to the steps to obtain the final product.

Example 2

The operating conditions and procedure were the same as in example 1, except that 30 parts of the powdered PBT obtained by freeze-grinding in step 1 were fed into the feed port of the twin-screw extruder together with the remaining 70 parts of the pelletized PBT.

Example 3

The operating conditions and procedure were the same as in example 1, except that 40 parts of the PBT powder obtained by freeze-grinding in step 1 was fed into the feed port of the twin-screw extruder together with the remaining 60 parts of the PBT pellets.

Example 4

The operating conditions and procedure were the same as in example 1, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 300. mu.m.

Example 5

The operating conditions and procedure were the same as in example 2, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 300. mu.m.

Example 6

The operating conditions and procedure were the same as in example 3, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 300. mu.m.

Example 7

The operating conditions and procedure were the same as in example 1, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 200. mu.m.

Example 8

The operating conditions and procedure were the same as in example 2, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 200. mu.m.

Example 9

The operating conditions and procedure were the same as in example 3, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 200. mu.m.

Example 10

The operating conditions and procedure were the same as in example 1, except that 10 parts of the powdered PBT obtained by freeze-grinding in step 1 were fed into the feed port of the twin-screw extruder together with the remaining 90 parts of the pelletized PBT.

Example 11

The operating conditions and procedure were the same as in example 1, except that 50 parts of the PBT powder obtained by freeze-grinding in step 1 were fed into the feed port of the twin-screw extruder together with the remaining 50 parts of the PBT pellets.

Example 12

The operating conditions and procedure were the same as in example 1, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 100. mu.m.

Example 13

The operating conditions and procedure were the same as in example 1, except that the powdered PBT obtained by freeze-grinding in step 1 had a D50 of about 500. mu.m.

Example 14

The operating conditions and procedure were the same as in example 1 except that in step 1 the resin was frozen at-90 ℃ for 10min and the resin in the frozen state was ground into PBT powder having a particle size D50 of about 400. mu.m using a grinder.

Example 15

The operating conditions and procedure were the same as in example 1 except that in step 1, the resin was frozen at-30 ℃ for 20min, and the resin in the frozen state was ground into PBT powder having a particle size D50 of about 400 μm using a grinder;

comparative example 1

The PBT material which is commonly used in the market and is subjected to solid phase tackifying is directly purchased from Suzhou British photoelectric material GmbH, and the trademark is PBT-61008.

Comparative example 2

Step 1: weighing 100 parts of PBT base resin with the intrinsic viscosity of 1.02dL/g, uniformly mixing the PBT base resin with 1.2 parts of chain extender MDI, 0.2 part of antioxidant AT10, 0.2 part of antioxidant 168 and 0.3 part of lubricant PETS for 5min, and feeding the mixture into a feeding port of a double-screw extruder;

step 2: adding 1.0 part of end capping agent hexamethylene diamine before an air exhaust section of a double-screw extruder to terminate the reaction; the large-area shallow threads are used for fully overflowing air bubbles in the air exhaust section of the double-screw extruder; the low molecules and bubbles are removed again in the vacuum degassing section of the twin-screw extruder with a high vacuum.

And step 3: and cooling, granulating, drying and packaging the extruded material strips according to the steps to obtain the final product.

Comparative example 2 is the PBT base resin of example 1 without freeze-grinding, otherwise the same as example 1.

Application exampleTesting of PBT Material Properties

The PBT materials obtained in the embodiment and the comparative example of the invention are tested with the following performance indexes:

intrinsic viscosity: intrinsic viscosity: the test was carried out according to ISO1628 standard, and a total of 15 samples were tested and averaged.

The CPK (Complex Process Capability index) index of intrinsic viscosity means the actual processing Capability of a Process under control over a certain period of time.

Reference to the formula for calculating CPK ("calculation of Process capability index CPK at modern technology level", encyclopedia, et al, "journal of electronic science and technology university of Western's republic of Western's computer (Nature science edition), Vol. 28, No. 4, p. 452-455):

CPK＝(T/6σ)*(1-|(X-U)/(T/2)|)

wherein σ is the standard deviation of the process parameter distribution, and X is the average of all sampled data; t is tolerance, namely specification upper limit-specification lower limit; u is the specification center value, i.e., (specification upper limit + specification lower limit)/2.

The larger the CPK value, the better the quality, and the CPK rating scale is shown in table 1 below:

TABLE 1

The properties of the PBT materials obtained in the examples according to the invention and in the comparative examples were tested according to the methods and criteria described above, and the results are shown in Table 2 below:

TABLE 2

The number of times of swelling was measured by trial using the PBT materials prepared in examples and comparative examples for 48 hours on the optical cable loose tube production line in the same process and recording the number of swelling.

The PBT prepared by the invention has high viscosity, the intrinsic viscosity is above 1.290dL/g, most embodiments are above 1.30dL/g, and the requirements of the PBT material for the optical cable can be met.

The products obtained in example 5 and comparative examples 1 and 2 were extruded in a Haake Torque rheometer in the same process at 235 deg.C, 245 deg.C, 270 deg.C, a head temperature of 260 deg.C, and a speed of 60 rpm. The torque change curve is recorded, as shown in fig. 1, it can be seen that the viscosity of the PBT material of example 5 is kept stable and the torque is always maintained in a relatively stable value range at high temperature, while the torque change of the PBT materials of comparative examples 1 and 2 is very large, especially the torque change of the PBT material of comparative example 2 is very large, which shows that the process of regrinding after freezing has a very important effect on the internal consistency of the PBT material. The viscosity stability of the PBT prepared by the comparative example is poor, and the swelling phenomenon is easy to occur when the PBT material is processed and manufactured on a loose tube production line for optical cables. According to the data in the table 2 and the data in fig. 1, it can be seen that the viscosity stability of the high-viscosity PBT product produced by the invention is obviously better than that of the product tackified by solid-phase tackifying and reaction tackifying by directly adding a chain extender, the intrinsic viscosity CPK of most examples is at a grade, the intrinsic viscosity CPK of the preferred examples reaches a + grade, and the evaluation grade of the CPK value of the PBT material obtained by the comparative example is poor or even unacceptable. The method provided by the invention can effectively improve the internal consistency of the PBT material, remarkably improve the viscosity stability, greatly reduce the bulge phenomenon when manufacturing the optical cable loose tube, and meet the increasingly strict requirements of the material on the market.

Meanwhile, as can be seen from table 2, other properties of the PBT material provided by the invention, such as mechanical strength, color and luster, and electrical properties, are not affected.

The above embodiments are merely illustrative of the present disclosure and do not represent a limitation of the present disclosure. Other variations of the specific structure of the invention will occur to those skilled in the art.

Claims

1. The high-viscosity PBT material for the optical cable comprises the following raw materials in parts by weight: 100 parts of PBT base resin and 0.5-3 parts of chain extender; is obtained by a preparation method comprising the following steps:

1)20-40 parts of PBT resin is frozen and ground into powder for later use; the temperature of freezing is between 50 ℃ below zero and 190 ℃ below zero, the freezing time is between 1 and 10 minutes, and the PBT powder with D50 of 100-

2. The high-viscosity PBT material for optical cables as claimed in claim 1, wherein the freezing temperature is from-90 ℃ to-130 ℃ and the freezing time is from 1 to 3 minutes.

3. The high-viscosity PBT material for optical cables as claimed in claim 1, wherein the PBT base resin has an intrinsic viscosity of 1.0 to 1.1dL/g, is particulate in an initial state, and is a PBT powder having a D50 of 200-400 μm.

4. The high-viscosity PBT material for optical fiber cables as claimed in claim 1, wherein the chain extender is a multipolymer of acrylate having a high reactive group.

5. The high-viscosity PBT material for optical fiber cables as claimed in claim 1, wherein the chain extender is an isocyanate, a bisoxazoline or a diepoxy compound.

6. The high-viscosity PBT material for optical fiber cables as claimed in claim 5, wherein said chain extender is at least one member selected from the group consisting of diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, and isophorone diisocyanate.

7. The high-viscosity PBT material for optical cables as claimed in claim 1, wherein said assistant further comprises 0.1-0.4 parts of antioxidant, 0.5-2.0 parts of end-capping reagent, and 0.3-0.8 parts of lubricant.

8. The high viscosity PBT material for optical cable of claim 7, wherein said antioxidant is at least one selected from the group consisting of pentaerythritol ester, triphosphite, dipentaerythritol diphosphite; and/or the lubricant is selected from at least one of pentaerythritol stearate and polyethylene wax; the end-capping reagent is ethylenediamine.

9. The high-viscosity PBT material for optical cable of claim 8, wherein the tetrapentaerythritol ester is antioxidant 1010, the triphosphite ester is antioxidant 168, and the dipentaerythritol diphosphite ester is antioxidant 626.

10. The high-viscosity PBT material for optical fiber cables as claimed in claim 1, wherein step (2) adopts a single-screw or twin-screw extruder, wherein a large-area shallow screw is adopted for the screw in the air exhaust section, and the screw pitch of the screw is 56mm-112 mm; the vacuum degree of the vacuum exhaust section is 100-500 Pa.

11. Use of a PBT material according to any of claims 1-10 for the manufacture of loose tubes for optical cables.