阅读说明：本技术 一种高耐候防水3m胶的制备工艺 (Preparation process of high-weather-resistance waterproof 3M adhesive ) 是由 秦高金 于 2021-07-16 设计创作，主要内容包括：本发明公开了一种高耐候防水3M胶的制备工艺,包括以下步骤：S1、称取120-150份清水、100-120份PVA溶液、250-300份醋酸乙烯、1-5份硫酸氢钠加入到反应容器中,所述反应容器配有调速搅拌器、回流管、滴液漏斗和温度计,启动调速搅拌器,转速为1000-1200r/min,并向反应容器中通入氦气30min,将反应容器内空气排空,关闭反应容器的出口,对反应容器进行加压至3Mpa,保压30min。本发明中,本发明3M胶水与市场上普通的3M胶水相比,其粘结强度更好,提升了3M胶水的性能,提高了钢板之间的粘接力,具有更好的应用技术效果,便于胶水的使用。(The invention discloses a preparation process of a high weather-resistant waterproof 3M adhesive, which comprises the following steps: s1, weighing 150 parts of 120-ion clear water, 120 parts of 100-ion PVA solution, 300 parts of 250-ion vinyl acetate and 1-5 parts of sodium bisulfate, adding the materials into a reaction container, wherein the reaction container is provided with a speed regulation stirrer, a return pipe, a dropping funnel and a thermometer, starting the speed regulation stirrer at the rotation speed of 1000-ion 1200r/min, introducing helium into the reaction container for 30min, evacuating air in the reaction container, closing an outlet of the reaction container, pressurizing the reaction container to 3Mpa, and maintaining the pressure for 30 min. Compared with the common 3M glue in the market, the 3M glue disclosed by the invention has the advantages that the bonding strength is better, the performance of the 3M glue is improved, the bonding force between steel plates is improved, the better application technical effect is achieved, and the glue is convenient to use.)

1. A preparation process of a high weather-resistant waterproof 3M adhesive is characterized by comprising the following steps:

s1, weighing and adding 120 parts by weight of clear water, 150 parts by weight of 100 parts by weight of PVA solution, 300 parts by weight of vinyl acetate and 1-5 parts by weight of sodium bisulfate into a reaction vessel, starting the speed-regulating stirrer at a rotation speed of 1000-1200r/min, stirring for 30min, introducing helium into the reaction vessel for 30min until air in the reaction vessel is exhausted, closing an outlet of the reaction vessel, pressurizing the reaction vessel to 3MPa, and maintaining the pressure for 30 min;

s2, introducing ethylene into the reaction container for 15min, evacuating helium in the reaction container, closing an outlet of the reaction container, then closing a valve to start heating, heating to 60 ℃, pressurizing the reaction container to 3Mpa, and maintaining the pressure for 30 min;

s3, adding 100-150 parts by weight of emulsion and 3-6 parts by weight of oxidant solution into a reaction container, starting a speed-regulating stirrer at the rotation speed of 600-800r/min, then preserving heat for 1h at 50-80 ℃, cooling to 30 ℃, emptying, discharging, standing and defoaming to obtain mixed emulsion;

s4, weighing 3-5 parts by weight of defoaming agent and 4-6 parts by weight of dispersing agent, adding into a reaction vessel, starting a speed-regulating stirrer at the rotation speed of 1000-1200r/min to uniformly mix the defoaming agent with the mixed emulsion, introducing nitrogen into the liquid for 30min, discharging bubbles formed after the nitrogen is completely contacted with the liquid, and introducing the nitrogen at the pressure of 0.1 Mpa;

s5, weighing 200-250 parts by weight of heavy calcium carbonate and 50-60 parts by weight of modified talcum powder, adding the heavy calcium carbonate and the modified talcum powder into a reaction container, and starting a speed-regulating stirrer at the rotating speed of 1000-1200 r/min;

s6, adding 40-60 parts by weight of plasticizer and 1-2 parts by weight of sterilization powder into the reaction vessel, and starting the speed-regulating stirrer at the rotation speed of 1000-1200r/min to obtain the 3M waterproof adhesive.

2. The process of claim 1, wherein in step S1, the PVA solution is prepared as follows:

weighing 10-15 parts by weight of PVA powder, putting the PVA powder into a first stirrer, stirring at the stirring speed of 1000-1200r/min while adding 8-12 parts by weight of 8-10% sodium lignosulfonate aqueous solution, stirring for 30min, adding 80-100 parts by weight of clear water for dilution, stirring for 15min, dropping a small amount of ammonia water, and adjusting the pH value of the solution to 7-8 to obtain the PVA solution.

3. The process for preparing the highly weather-resistant waterproof 3M adhesive according to claim 2, wherein in step S3, the preparation method of the emulsion is as follows:

weighing 25-40 parts by weight of PVA solution, pouring the PVA solution into a second stirrer, stirring at the stirring speed of 1000r/min for 15min while adding 150 parts by weight of 230 parts by weight of vinyl acetate, adding 2-5 parts by weight of op-10 emulsifier, stirring for 15min, adding 130 parts by weight of 170 parts by weight of clear water, stirring for 15min, and passing the mixture for 3 times under the pressure of 900Pa by using a homogenizer to obtain the emulsion with the average particle size of 220-240 mm.

4. The process of claim 3, wherein in step S3, the oxidant solution is prepared as follows:

weighing 4-5 parts by weight of oxidant, pouring into a third stirrer, adding 90-100 parts by weight of clear water, and uniformly stirring at the stirring speed of 1000r/min and 800-.

5. The process for preparing high weather-resistant waterproof 3M adhesive according to claim 4, wherein the oxidant is tert-butyl hydroperoxide.

6. The preparation process of the highly weather-resistant waterproof 3M adhesive according to claim 5, wherein in step S5, the preparation method of the ground calcium carbonate is as follows:

A. crushing calcite by using a crusher to obtain calcium carbonate particles with the particle diameter of less than 3 mm;

B. fully mixing calcium carbonate particles, water and a dispersing agent, and soaking the slurry for 30-40 min;

C. putting the slurry into a ball mill for wet grinding, adding antioxidant and mica powder, wherein the linear speed of the stirrer is 2-3m/s, and the grinding time is 15-30 min;

D. putting the slurry into a stirring type grinder for wet grinding, wherein the linear velocity of the stirrer is 5-7m/s, and the grinding time is 25-30 min;

E. and spray drying the slurry and propylene glycol by using spray drying equipment at the drying temperature of 150 ℃ and 200 ℃ to obtain the heavy calcium carbonate powder.

7. The process for preparing high weather-resistant waterproof 3M adhesive according to claim 6, wherein in the step C, the antioxidant is hindered phenol antioxidant.

8. The preparation process of the high weather-resistant waterproof 3M adhesive according to claim 1, wherein in step S5, the preparation method of the modified talc powder is as follows:

A. adding 80-90 parts by weight of talcum powder, 1-2 parts by weight of coupling agent and 0.5-1 part by weight of active agent into a high-speed mixing stirrer, and mixing and dispersing at the rotating speed of 600-;

B. adding the premix, 1-5 parts by weight of expanding agent and 1-3 parts by weight of foaming agent into a closed dispersing mixer, controlling the temperature of the dispersing mixer to be 60-100 ℃, dispersing and mixing at the speed of 400-l000rpm, simultaneously starting vacuum negative pressure, dispersing for 10-20min, and uniformly dispersing the expanding agent and the foaming agent in a talcum powder layered structure to obtain an intercalation premix;

C. and adding the intercalated premix into a multistage millstone type mixing mill, setting the rotating speed of the multistage millstone type mixing mill at 200-140 rpm and the temperature at 120-140 ℃, generating micro-bubble rapid expansion under the synergistic action of an expanding agent and a foaming agent, and stripping the talcum powder by high tension, and further utilizing the shearing stripping action of the multistage millstone type mixing mill to strip the talcum powder to obtain the modified talcum powder.

Technical Field

The invention relates to the technical field of glue preparation processes, in particular to a preparation process of a high-weather-resistance waterproof 3M glue.

Background

The 3M glue is a common adhesive in life, is widely applied to bonding of plastics, metals, rubber, ceramics, wood, electronic elements, leather, paper and the like, can also be used for filling tooth cavities and the like, such as bonding of internal parts of instrument panel decorative plastic parts and the like, and has the advantages of quick bonding, good bonding strength and good high and low temperature resistance, so that the application is wide.

The weather resistance of the glue is the performance of the glue subjected to outdoor weather tests, such as comprehensive damage caused by illumination, cold and hot conditions, wind and rain, bacteria and the like, and the tolerance capability of the glue is called weather resistance, however, the 3M glue in the prior art has poor weather resistance and is inconvenient to use.

Disclosure of Invention

In order to solve the technical problems mentioned in the background technology, a preparation process of a high weather-resistant waterproof 3M adhesive is provided.

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

a preparation process of a high weather-resistant waterproof 3M adhesive comprises the following steps:

s1, weighing 150 parts of clear water, 120 parts of PVA solution, 300 parts of vinyl acetate and 1-5 parts of sodium bisulfate in parts by weight, adding the clear water, the PVA solution, the vinyl acetate and the sodium bisulfate into a reaction container, wherein the reaction container is provided with a speed regulation stirrer, a return pipe, a dropping funnel and a thermometer, starting the speed regulation stirrer at a rotation speed of 1000 + 1200r/min, stirring for 30min, introducing helium into the reaction container for 30min until the air in the reaction container is exhausted, closing an outlet of the reaction container, pressurizing the reaction container to 3Mpa, and maintaining the pressure for 30 min;

s2, introducing ethylene into the reaction container for 15min, evacuating helium in the reaction container, closing an outlet of the reaction container, then closing a valve to start heating, heating to 60 ℃, pressurizing the reaction container to 3Mpa, and maintaining the pressure for 30 min;

s3, adding 100-150 parts by weight of emulsion and 3-6 parts by weight of oxidant solution into a reaction container, starting a speed-regulating stirrer at the rotation speed of 600-800r/min, then carrying out heat preservation at 50-80 ℃ for 1h, cooling to 30 ℃, emptying, discharging, standing and defoaming to obtain a mixed emulsion;

s4, weighing 3-5 parts of defoaming agent and 4-6 parts of dispersing agent according to parts by weight, adding the mixture into a reaction vessel, starting a speed-regulating stirrer at the rotation speed of 1000-1200r/min to uniformly mix the mixture with the mixed emulsion, introducing nitrogen into the liquid for 30min, discharging bubbles formed after the nitrogen is completely contacted with the liquid, and introducing the nitrogen at the pressure of 0.1 MPa;

s5, weighing 200-250 parts of heavy calcium carbonate and 50-60 parts of modified talcum powder according to the parts by weight, adding the heavy calcium carbonate and the 50-60 parts of modified talcum powder into a reaction vessel, and starting a speed regulating stirrer at the rotating speed of 1000-1200 r/min;

s6, adding 40-60 parts by weight of plasticizer and 1-2 parts by weight of sterilization powder into the reaction vessel according to the parts by weight, and starting the speed-regulating stirrer at the rotation speed of 1000-1200r/min to obtain the 3M waterproof adhesive.

As a further description of the above technical solution:

in step S1, the PVA solution is prepared as follows:

weighing 10-15 parts by weight of PVA powder, putting the PVA powder into a first stirrer, stirring at the stirring speed of 1000-1200r/min while adding 8-12 parts by weight of 8-10% sodium lignosulfonate aqueous solution, stirring for 30min, adding 80-100 parts by weight of clear water for dilution, stirring for 15min, dropping a small amount of ammonia water, and adjusting the pH value of the solution to 7-8 to obtain the PVA solution.

As a further description of the above technical solution:

in step S3, the emulsion is prepared as follows:

weighing 25-40 parts by weight of PVA solution, pouring the PVA solution into a second stirrer, stirring at the stirring speed of 1000r/min for 800-.

As a further description of the above technical solution:

in step S3, the oxidant solution is prepared as follows:

weighing 4-5 parts of oxidant by weight, pouring the oxidant into a third stirrer, adding 90-100 parts of clear water by weight, and uniformly stirring at the stirring speed of 1000r/min under 800-.

As a further description of the above technical solution:

the oxidizing agent is tert-butyl hydroperoxide.

As a further description of the above technical solution:

in step S5, the preparation method of the ground calcium carbonate is as follows:

A. crushing calcite by using a crusher to obtain calcium carbonate particles with the particle diameter of less than 3 mm;

B. fully mixing calcium carbonate particles, water and a dispersing agent, and soaking the slurry for 30-40 min;

C. putting the slurry into a ball mill for wet grinding, adding antioxidant and mica powder, wherein the linear speed of the stirrer is 2-3m/s, and the grinding time is 15-30 min;

D. putting the slurry into a stirring type grinder for wet grinding, wherein the linear velocity of the stirrer is 5-7m/s, and the grinding time is 25-30 min;

E. and spray drying the slurry and propylene glycol by using spray drying equipment at the drying temperature of 150 ℃ and 200 ℃ to obtain the heavy calcium carbonate powder.

As a further description of the above technical solution:

in step C, the antioxidant is a hindered phenolic antioxidant.

As a further description of the above technical solution:

in step S5, the modified talc powder is produced by the method comprising:

A. adding 80-90 parts by weight of talcum powder, 1-2 parts by weight of coupling agent and 0.5-1 part by weight of active agent into a high-speed mixing stirrer, and mixing and dispersing at the rotating speed of 600-;

B. adding the premix, 1-5 parts by weight of expanding agent and 1-3 parts by weight of foaming agent into a closed dispersing mixer, controlling the temperature of the dispersing mixer to be 60-100 ℃, dispersing and mixing at the speed of 400-l000rpm, simultaneously starting vacuum negative pressure, dispersing for 10-20min, and uniformly dispersing the expanding agent and the foaming agent in a talcum powder layered structure to obtain an intercalation premix;

C. and adding the intercalated premix into a multistage millstone type mixing mill, setting the rotating speed of the multistage millstone type mixing mill at 200-140 rpm and the temperature at 120-140 ℃, generating micro-bubble rapid expansion under the synergistic action of an expanding agent and a foaming agent, and stripping the talcum powder by high tension, and further utilizing the shearing stripping action of the multistage millstone type mixing mill to strip the talcum powder to obtain the modified talcum powder.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. compared with the common 3M glue in the market, the 3M glue prepared by the process disclosed by the invention has better bonding strength, improves the performance of the 3M glue, improves the bonding force between steel plates, has a better application technical effect, and is convenient to use.

2. In the invention, the performance of common 3M glue in the market is weakened by about 50% after being irradiated by ultraviolet light for 300h, the performance of the 3M glue prepared by the process is weakened by about 30% after being irradiated by the ultraviolet light for 300h, and compared with the common 3M glue in the market, the 3M glue prepared by the process has stronger ultraviolet irradiation resistance, better weather resistance and convenience for use.

3. In the invention, the performance of common 3M glue in the market is weakened by about 60% after the glue is subjected to a high temperature of 240h, however, the performance of the 3M glue prepared by the process is weakened by about 50% after the glue is subjected to a high temperature of 240h, and compared with the common 3M glue in the market, the 3M glue prepared by the process has stronger high temperature resistance, better high temperature resistance and convenience for use of the glue.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Examples

The invention provides a technical scheme that: a preparation process of a high weather-resistant waterproof 3M adhesive, which adopts the material proportion in parts by weight, comprises the following steps:

s1, weighing 150 parts of 120-ion clear water, 120 parts of 100-ion PVA solution, 300 parts of 250-ion vinyl acetate and 1-5 parts of sodium bisulfate, adding the materials into a reaction container, wherein the reaction container is provided with a speed regulation stirrer, a return pipe, a dropping funnel and a thermometer, starting the speed regulation stirrer at the rotation speed of 1000-ion 1200r/min, stirring for 30min, introducing helium into the reaction container for 30min until the air in the reaction container is exhausted, closing the outlet of the reaction container, pressurizing the reaction container to 3Mpa, and maintaining the pressure for 30 min;

s2, introducing ethylene into the reaction container for 15min, evacuating helium in the reaction container, closing an outlet of the reaction container, then closing a valve to start heating, heating to 60 ℃, pressurizing the reaction container to 3Mpa, and maintaining the pressure for 30 min;

s3, adding 150 parts of emulsion and 3-6 parts of oxidant solution into a reaction container, starting a speed-regulating stirrer at the rotation speed of 600-;

s4, weighing 3-5 parts of defoaming agent and 4-6 parts of dispersing agent, adding into a reaction vessel, starting a speed-regulating stirrer at the rotation speed of 1000-;

s5, weighing 200-250 parts of heavy calcium carbonate and 50-60 parts of modified talcum powder, adding the materials into a reaction container, and starting a speed-regulating stirrer at the rotation speed of 1000-1200 r/min;

s6, adding 40-60 parts of plasticizer and 1-2 parts of sterilization powder into the reaction vessel, starting the speed-regulating stirrer at the rotation speed of 1000-1200r/min, and obtaining the 3M waterproof adhesive.

The preparation method of the PVA solution is as follows:

weighing 10-15 parts of PVA powder, placing the PVA powder into a first stirrer, stirring at the stirring speed of 1000-1200r/min while adding 8-12 parts of 8-10% sodium lignosulfonate aqueous solution, stirring for 30min, adding 80-100 parts of clear water for diluting, stirring for 15min, dropping a small amount of ammonia water, and adjusting the pH value of the solution to 7-8 to obtain the PVA solution.

The preparation method of the emulsion comprises the following steps:

weighing 25-40 parts of PVA solution, pouring the PVA solution into a second stirrer, stirring at the stirring speed of 1000r/min for 800-.

The oxidant solution was prepared as follows:

weighing 4-5 parts of oxidant, pouring into a third stirrer, adding 90-100 parts of clear water, and uniformly stirring at the stirring speed of 800-1000r/min to obtain an oxidant solution.

The oxidizing agent is t-butyl hydroperoxide.

In step S5, the ground calcium carbonate is prepared as follows:

A. crushing calcite by using a crusher to obtain calcium carbonate particles with the particle diameter of less than 3 mm;

B. fully mixing calcium carbonate particles, water and a dispersing agent, and soaking the slurry for 30-40 min;

C. putting the slurry into a ball mill for wet grinding, adding antioxidant and mica powder, wherein the linear speed of the stirrer is 2-3m/s, and the grinding time is 15-30 min;

D. putting the slurry into a stirring type grinder for wet grinding, wherein the linear velocity of the stirrer is 5-7m/s, and the grinding time is 25-30 min;

E. and spray drying the slurry and propylene glycol by using spray drying equipment at the drying temperature of 150 ℃ and 200 ℃ to obtain the heavy calcium carbonate powder.

In step C, the antioxidant is a hindered phenolic antioxidant.

In step S5, the modified talc powder is produced by the method comprising:

A. adding 80-90 parts by weight of talcum powder, 1-2 parts by weight of coupling agent and 0.5-1 part by weight of active agent into a high-speed mixing stirrer, and mixing and dispersing at the rotating speed of 600-;

B. adding the premix, 1-5 parts by weight of expanding agent and 1-3 parts by weight of foaming agent into a closed dispersing mixer, controlling the temperature of the dispersing mixer to be 60-100 ℃, dispersing and mixing at the speed of 400-l000rpm, simultaneously starting vacuum negative pressure, dispersing for 10-20min, and uniformly dispersing the expanding agent and the foaming agent in a talcum powder layered structure to obtain an intercalation premix;

C. and adding the intercalated premix into a multistage millstone type mixing mill, setting the rotating speed of the multistage millstone type mixing mill at 200-140 rpm and the temperature at 120-140 ℃, generating micro-bubble rapid expansion under the synergistic action of an expanding agent and a foaming agent, and stripping the talcum powder by high tension, and further utilizing the shearing stripping action of the multistage millstone type mixing mill to strip the talcum powder to obtain the modified talcum powder.

And (3) tensile test:

taking 24 steel plates with the size of 150 mm-150 mm and the thickness of 10mm, wherein each group comprises 12 steel plates and is divided into a large group A and a large group B, each large group comprises 6 small groups, and each small group comprises 2 steel plates, namely the large group A comprises a1 small group, a2 small group, a3 small group, a4 small group, a5 small group and a6 small group;

the two steel plates of the a1 group, the a2 group, the a3 group, the a4 group, the a5 group and the a6 group are bonded by using common 3M glue;

the B major component is B1 subgroup, B2 subgroup, B3 subgroup, B4 subgroup, B5 subgroup and B6 subgroup;

the two steel plates of the b1, b2, b3, b4, b5 and b6 groups are bonded by using the 3M glue prepared by the process;

when 3M glue is used for bonding, the glue is uniformly coated on the steel plate, and the coating area is the whole side surface of the steel plate;

the performance of the glue can be evaluated by measuring the tension when the two steel plates are pulled apart by a tension machine; the test data are as follows:

according to experimental data, compared with the common 3M glue in the market, the 3M glue prepared by the process disclosed by the invention has the advantages that the bonding strength is better, the performance of the 3M glue is improved, the bonding force between steel plates is improved, the application technical effect is better, and the use of the glue is convenient.

Weather resistance test

Taking 24 steel plates with the size of 150 mm-150 mm and the thickness of 10mm, wherein each group comprises 12 steel plates and is divided into a large group A and a large group B, each large group comprises 6 small groups, and each small group comprises 2 steel plates, namely the large group A comprises a1 small group, a2 small group, a3 small group, a4 small group, a5 small group and a6 small group;

the two steel plates of the a1 group, the a2 group, the a3 group, the a4 group, the a5 group and the a6 group are bonded by using common 3M glue;

the B major component is B1 subgroup, B2 subgroup, B3 subgroup, B4 subgroup, B5 subgroup and B6 subgroup;

the two steel plates of the b1, b2, b3, b4, b5 and b6 groups are bonded by using the 3M glue prepared by the process;

when 3M glue is used for bonding, the glue is uniformly coated on the steel plate, and the coating area is the whole side surface of the steel plate;

the A large group and the B large group are placed in a test box, an ultraviolet lamp is used for irradiating in the test box (the ultraviolet lamp is mainly ultraviolet light near 313nm and 340nm in wavelength and has no visible light), and the A large group and the B large group are taken out after irradiation for 300h for carrying out tension test:

the performance of the glue can be evaluated by measuring the tension when the two steel plates are pulled apart by a tension machine; the test data are as follows:

according to experimental data, the performance of common 3M glue in the market is weakened by about 50% after being irradiated by ultraviolet light for 300 hours, the performance of the 3M glue prepared by the process is weakened by about 30% after being irradiated by the ultraviolet light for 300 hours, and compared with the common 3M glue in the market, the 3M glue prepared by the process has stronger ultraviolet irradiation resistance, better weather resistance and convenience for use.

High temperature test

Taking 24 steel plates with the size of 150 mm-150 mm and the thickness of 10mm, wherein each group comprises 12 steel plates and is divided into a large group A and a large group B, each large group comprises 6 small groups, and each small group comprises 2 steel plates, namely the large group A comprises a1 small group, a2 small group, a3 small group, a4 small group, a5 small group and a6 small group;

the two steel plates of the a1 group, the a2 group, the a3 group, the a4 group, the a5 group and the a6 group are bonded by using common 3M glue;

the B major component is B1 subgroup, B2 subgroup, B3 subgroup, B4 subgroup, B5 subgroup and B6 subgroup;

the two steel plates of the b1, b2, b3, b4, b5 and b6 groups are bonded by using the 3M glue prepared by the process;

when 3M glue is used for bonding, the glue is uniformly coated on the steel plate, and the coating area is the whole side surface of the steel plate;

the A large group and the B large group are placed in a high-low temperature test box, the temperature in the test box is adjusted to 80 ℃, and the A large group and the B large group are taken out after 240 hours for a tension test:

the performance of the glue can be evaluated by measuring the tension when the two steel plates are pulled apart by a tension machine; the test data are as follows:

according to experimental data, the performance of the common 3M glue in the market is weakened by about 60% after the common 3M glue is subjected to high temperature for 240 hours, however, the performance of the 3M glue prepared by the process is weakened by about 50% after the common 3M glue is subjected to high temperature for 240 hours, and compared with the common 3M glue in the market, the 3M glue prepared by the process has the advantages of strong high temperature resistance, better high temperature resistance and convenience in glue use.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.